A damage focused essence build is recommended because of the low incoming damage, with Evangelism being able to mostly take care of it on its own.
The healing relevant part is mostly P1. Keep your Radiances for Incineration and Gale Blast. Coordinate with your other healers how you take care of them, and look to use your Evangelism when these abilities happen close to each other. Take special note of these timings and plan your Radiances accordingly, try to have 2 available when they hit close to each other.
In P2 the healing requirement is very low if your raid does what it needs to.
A healing oriented essence build is recommended for this boss because of the large healing requirement in phase 2 of the boss.
This fight is broken up into 2 very distinct phases. In phase 1, keep track of the Consuming Shadows dot happening throughout the phase, it will start out weak but ramp up as the phase goes on. When you hide in the void zones, the raid will take a small amount of damage, so make use of radiances here since there isn't much damage in P1.
During P2, Maut will channel Obsidian Shatter, reflecting a portion of all the damage players deal to the boss from the Obsidian Skin. This is a long phase, so coordinate with your healers when you use your cooldowns since the damage taken is really high. Forbidden Ritual will send orbs towards the boss from the edges of the room, but when taken by a player they deal a large amount of raid damage but also gives a buff that significantly increase your healing and mana regeneration, so be sure to have your ramps done before this buff is acquired. Along with this, there is also Drain Essence, which is a dot that will need to be dispelled quickly after the player with it has gone out of the raid. When dispelled, it deal high raid damage, so plan when and who dispels it and be ready with a cooldown.
The Prophet Skitra
A damage focused essence build is recommended because of the highly condensed, moderate damage intake and the focus on killing the Illusion during P2.
In phase 1, the most notable damage intake is the add spawned by Shred Psyche. After a few seconds, an add will spawn on top of the target that had the debuff. This add will cast Psychic Outburst, which will deal a large amount of raid damage that needs to be healed. After this, until killed, the add will continue doing pulsing damage every second, so focus your Evangelism and Raptures on these add casts. Plan out your radiances and how you want to use them in conjunction with Evangelism and Radiance. There will be spawned adds that walk towards you, killing you if you're touched, but as a discipline priest you can use the talent Shining Force to crowd control them, giving your raid more space to work with.
In phase 2, there will be constant low ticking damage that ramps up the longer the phase goes on. This damage is fairly low, so you should mainly focus on damaging down the spawned Illusion while occasionally healing with radiances.
Dark Inquisitor Xanesh
A damage focused essence build is recommended because of the generally low healing requirement of the fight. Damage intake is low and the additional healing isn’t required.
A 1 phase encounter that is mechanically dense but very light on healing requirements. Heal the players that get the copy, raid takes consistent damage throughout the entire encounter but its very low. Your job will be to keep the raid topped from the Soul Flay as well as the constant ticking damage from Anguish. The overall healing requirement of this fight is very low, and is based on wave damage with half the raid taking the Soul Flay damage every so often.
A healing oriented setup is recommended, since there is high amounts of both scripted and unscripted damage that needs to be dealt with consistently.
Throughout the fight, the bosses will swap as to who is in control of the hivemind, having different abilities depending on whos in control, and when the control is swapped the entire raid will be hit by Devouring Frenzy, which deals a large amount of damage over 12 seconds. Have your Evangelism and radiances ready for whenever this damage comes out as its the hardest hitting part of the fight.
There is also a myriad of smaller amounts of damage happening from the adds to most of the players of the raid, both melee, aoe pulses and dots, so be ready to spread atonements when necessary and keep an eye on when you need to use your spare Radiance charge or Rapture. The biggest healing parts are very predictable, so base your radiances and schisms on those and play around with what is left over.
Shad'har the Insatiable
A damage oriented setup is recommended, since the healing requirement isn’t high enough to require healing essences and will most likely end up as a damage race. If healing is becoming a problem for your guild, change to a healing setup.
Your main points will be focusing on the phase based AoE damage intakes, as as taking care of the strong dots being applied periodically to a few players throughout the encounter.
Umbral Mantle is the umbral phases AoE damage, and is just a constantly pulsing aoe damage throughout the phase.
In the entropic phase, the boss does ticking aoe damage with Entropic Mantle, as well as players getting some nasty dots from soaking the zones the boss spawns. Entropic Mantle keeps ramping up in damage as the encounter goes on, so you need to be more and more aware as the phase goes on.
Lastly, the noxious phase has Noxious Mantle, which does slightly slower but harder hitting constant raid damage.
Because of the large, rather consistent aoe damage going out on this encounter, alongside the very condensed heavy hitting aoe, healing focused essences are recommended.
Every so often, when the boss’ energy reaches 100, Drest’agath will cast Throes of Agony, dealing a lot of raid wide aoe damage, which needs to be dealt. Coordinate with your healing team about where each cooldown goes, but be ready to supplement the healing cooldown with extra radiance charges. Spread out your evangelism and rapture between these to do powerful efficient healing to them.
Additionally, the appendages will do various abilities, dealing varied damage to your raid group that needs to be dealt with efficiently between Throes of Agony casts.
The boss also casts Entropic Crash, dealing large falloff aoe damage to the raid every so often. When this overlaps with Throes of Agony, the damage will be extremely high, so keep an eye on your timers and potentially overlap Rapture and Evangelism to deal with this.
Be sure to spread plenty of dots around the adds, since this will significantly increase your atonement healing.
Healing essences is recommended because of the large amount of damage the dispelling will cause, resulting in a significant healing check.
On heroic, there is not a lot to heal in general on this fight. During P1 there is nothing to really heal, so just focus on dps, while in P2 when you kill the Blood of Ny’alotha raid wide damage is dealt.
On mythic, the Cursed Blood debuff that creates a circle around players in P2 is now happening in both phases, is dispellable and slowly shrinks. When you dispel these, a large amount of damage is dealt. Playing and planning smartly around the dispels as a guild is essential, and your cooldowns will be planned in accordance with when and how your guild decides to dispel these. Power Word: Barrier can prove very powerful here, as well as splitting up your Evangelism and Rapture ramps. When planning your healing, be sure to spread Purge the Wicked to as many targets as possible, generating a lot of extra healing when it's necessary.
If tank damage continues being extremely high, playing a healing focused setup with either Vitality Conduit or Spirit of Perseverance will be the optimal essence setup. If tank damage gets tuned back, going into a more general healing setup is recommended for the phase 3 healing check.
Tanks will be afflicted by Despair, a heavy hitting dot that will eventually explode and hit the raid for a large portion of the tanks remaining health, so keeping them healthy during this dot is extremely vital. Additionally, be ready to dispel the Annihilation from the tank, reducing their overall healing required. On testing, the tank damage was by far the hardest healing requirement of the fight, but it will likely be nerfed going into live servers.
For raid healing, there will be a lot of varied damage coming from add casts and targeting. When the boss reaches 40%, P3 will begin and everyone in the raid will be taking a lot of ticking damage. The damage will ramp up as the phase goes on, and it becomes a healing and damage check. Be sure you have a lot of mana and all your cooldowns available when P3 begins, as this is the large brunt of the healing requirement for the fight.
On mythic, a new add spawns that grips people, and during the breath phase your Life Grip can be vital in saving someone who got gripped at a bad moment.
Ra-den the Despoiled
Healing essences are recommended, both for the very hard hitting orbs as well as the last 40% of the boss, which has very high healing demands.
When orbs connect with the boss, they do raid damage in a few different ways. When the lightning orb hits, it deals a lot of raw damage to the entire raid. When the shadow orb hits, it will apply a large healing absorb and slight dot to the raid. On mythic there is an extra ball, the nightmare ball, and you have to deal with 2 orb explosions at the same time. The nightmare orb will apply a heavy hitting dot that will chain around the raid until it fizzles out. Having to deal with 2 of these effects at once can be quite hard hitting, so be ready to ramp very heavily and use your Shadowfiend.
Once Ra-den reaches 40%, phase 2 will begin and he will cast Ruin, dealing raid wide damage throughout the phase every 2 seconds. These last 40% of the boss will be the most healing intensive part of it, and CDs will most likely be chained. Getting your Evangelism rolling early on in the phase and using Rapture independently to cover other parts is heavily advised. Plan this phase very heavily with your guild.
Carapace of N'Zoth
Although no mythic testing has been done and we therefore lack information, going with a healing focused essence build is likely because of the amount of damage that happens in P3. If the damage turns out to be on the lax side, swapping to a damage focused setup can be advised.
This encounter has not been tested on mythic, and figuring out how to correctly play this encounter is therefore harder.
The adds spawned will deal differing amounts of damage to the raid, but nothing serious, just keep an eye on the players.
The Gaze of Madness add deals damage to a few players while channeling, and deals a moderate amount of raid damage when killed, so be ready to heal up the players who took the extra damage while doing aoe healing.
During P2, when you’re on the inside, players running up the sides. The damage is light but constant, so dot up the cysts and throw out some shields while moving. Getting to the Fury of N’zoth, he will deal a large amount of aoe damage, so make sure people are healed up when you engage him.
Getting to phase 3, the boss will apply Insanity Bombs periodically to everyone in the raid. These bombs will explode and deal a large amount of damage to the raid. These bombs are extremely telegraphed, so prepare accordingly with planned out radiance charges. There is a lot of adds in this fight, so make ample use of your dots and the penance cleave.
Remember that this encounter was only tested on heroic, so the fight might end up being significantly different on mythic.
N'Zoth the Corruptor
For what testing has been done, the heroic version is very light on damage, so damage focused essences are recommended so you can hit the damage checks in the mind phases. However, the mythic encounter should be significantly harder on healing, so be ready to adapt and change to healing essences.
Just like Carapace of N’zoth, this encounter was not tested much, and was not tested on mythic difficulty. Information is therefore limited, and might change.
During the first 2 phases, the damage done to the raid is incredibly light.
During P2, the boss does a constant small amount of damage to the entire raid. Be ready to spot heal players with the Paranoia debuff, as they will take a very large amount of damage very quickly until they find each other. Be sure to dispel the Corrupted Mind debuff if they don't get interrupted to avoid players losing sanity. There will also be an assortment of relatively random damage coming from the different tentacles to the raid group.
When you're sent inside the mind realm in P2, players will take damage when moving, so coordinate things like Rapture with moving while dotting up multiple targets.
In P3, Paranoia will continue, but Evoke Anguish will also be applied, which is a very heavy dot that needs to be spot healed. The boss is generally untested and the mythic version will most likely be significantly different when it comes to healing, so be sure to follow the Race to World First event to keep up with how N’zoth will end up playing out on mythic.
Crucible of Storms
The Restless Cabal
Battle of Dazar'alor
Champion of the Light
Grong, the Jungle Lord
This fight is the typical two target boss fight where Purge the Wicked does an excellent job.
Pay attention to the debuffs called Searing Embers and dispel as quickly as possible to prevent the avoidable damage. Mass dispel if the players are stacked is the best thing you can do. Prioritize targets who are focused by the Spirits of Xuen.
As a healer the most important part in the first phase is the third room (70%-60% boss hp) and the fourth room (60%-50%). During the third room the group will be taking a lot of AOE damage and using Shadowfiend and Evangelism can be worth.
In the fourth room 2 people will get a debuff called Hex of Lethargy and they will require a dispel using Purify or Mass Dispel. If they don’t get dispelled every movement will cause them to take a stacking debuff which becomes really hard to heal after 2 stacks. Well timed Mass Dispel can dispel both at the same time.
Another important thing to pay attention to is how to use the gems correctly. If you take the Amethyst of the Shadow King your heals apply a debuff called Shadow-Touched which reduces the shadow damage taken significantly. A player missing the debuff will take a lethal damage and even die on Heroic/Mythic difficulty. Make sure to apply the debuff to everyone especially in phase 2 during the Wail of Greed cast.
Conclave of the Chosen
The biggest two sources of incoming damage on this fight are from the debuff Cry of the Fallen (which occurs every time one of the Aspects die) and Pa’ku’s Wrath. Coordinate with your other healers how are you going to use your raid cooldowns. Saving a barrier for Pa’ku’s Wrath can prevent a lot of damage, since the raid is stacked in the circle.
After Akunda's Aspect enters the fight, she will periodically cast Mind Wipe on random players which will silence them until they get dispelled. Pay attention to those debuffs and dispel them as quickly as possible.
During this fight the most important ability to watch for is the Scorching Detonation cast, which occurs periodically and causes a heavy AOE damage to the raid based on the distance between them and the tank taking the cast. This mechanic persists during all of the phases.
During Phase one pay attention to the people who get Grievous Axe, the debuff causes the players to bleed until they’re healed above 90%. Be sure to top them off quickly.
During Phase two make sure to top off the tank tanking Bwonsamdi, before they take the Caress of Death cast on them. That debuff will prevent them from being healed during the debuff duration and cannot be dispelled.
After reaching Phase three the fight continues in two realms. Disc priest are extremely useful in the Death realm, because moving to the next Phase happens when Bwonsamdi reaches 50%. If you’re in the Death realm blow all your DPS cooldowns and nuke the boss during Bloodlust. A very important thing to pay attention to is that in the Death realm people will be taking passive aoe damage from a debuff called Deathly Withering. It can be very dangerous on high amount of stacks because Bwonsamdi will cast the Caress of Death debuff on random targets, preventing them from being healed. Clearing the stacks by walking through one of the Death Rifts, after getting the debuff, is the best thing to do.
High Tinker Mekkatorque
It is the heaviest AOE damage during the first phases of the fight. Top off players who have Gigavolt Charge. Apply Atonement before they line of sight you because healing through Atonement has no line of sight requirement.
On Mythic difficulty Wormhole Generator also Discombobulates 3 people which will require a dispel or they are going to get crushed by the following Crash down. Also a few more people will get sent into the air by Miscalculated Teleport and if they don’t have a movement ability that prevents fall damage, using Leap of Faith on them will save them.
In the last phase the fight just becomes more dangerous. The boss gains more damage which makes it really hard for the tanks, so keep an eye on them. Also there will be fire you need to dodge from the Exploding Sheep, which can make the last phase movement intense.
This fight takes place in two boats with two different bosses which switch on 50%. Phase one is one of the most healing intense fights in this tier, so that means we shouldn’t hold back our cooldowns and use them in phase one, but not just mindlessly blow them, instead rotating them.
While healing the Sister Katherine’s boat
Pay attention to where the Crackling Lightning is being dropped and move away from it. Putting distance between yourself and the debuff will reduce the silence duration on you.
While healing the Brother Joseph’s boat
Pay attention to the Tempting Song cast from the Sirens. A Leap of Faith grip might be required based on the position of the player. Also pay attention to the players being charmed, since they will be moving through Sea Storms which will slow them and deal damage.
During phase two the raid damage is significantly lower and requires less healing but better target selection. Top of the player who is soaking Ire of the Deep. On Mythic difficulty some of the mechanics from phase one continue during phase two. Pay attention to the sirens since there will be more than one, helping with the DPS might be required.
Lady Jaina Proudmoore
There are several extra things you can dot on this fight; Players who are Frozen Solid, Frozen Ballistas, Unexploded Ordnances and Jaina's Tide Elemental. Having several dots out when you're ramping up for this fight is a pretty big HPS increase.
Focus your Power Word: Radiances at the latest 10 seconds before you pop Ordnances to reset stacks. Make plenty use of Shadow Mend on this fight, even more so than normally. If you're standing still and Rapture isn't active, you should not be casting Power Word: Shield.
Start out P1 with a Shadowfiend purely for DPS, it will be up again for the start of P2 when you need the healing, and then again for big P3 healing, don't save it for healing at any point in P1.