Talent Builds
Single Target
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This is the standard ST build as of the time of writing this.
Wither can be maintained without using the global on it with soulfire, cataclysm, and channel demonfire. Spend shards on bolts while maintaining roaring blaze uptime, try to keep soulfire, channel demonfire and cataclysm on cd while not overcapping soul shards.
Cleave
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This build is basically the same as the Single Target build with the exception of havoc in place of demonfire mastery. The playstyle is very similar to the Single target build however you can save cata for when you need to apply wither to multiple targets.
Mythic+
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The combination of cataclysm + channel demonfire allows you to maintain 100% uptime of wither on all the mobs in the pack. This leads to a very smooth gameplay with lots of shard generation, allowing for the classic rain of fire spam outside of using cata/cdf on cd.
Class Talents
The warlock class tree is very cookie cutter, (you take X talent point because it gives you a throughput/survivability increase) as in you only have 1-2 flexible points, those are Fiendish Stride and arguably Fel Domination. Soulburn is a unique ability that consumes a shard and empowers your next utility spell, often this is used in combination with either healthstone or demonic circle making your healthstone heal for more or your portal giving a sprint and a freedom effect. Soulburn Gateway can be used if you need to place a gateway in the middle of combat and you have excess shards.
I do not recommend dropping fel domination, whereas, fiendish stride is quite a weak node and therefore can be dropped for something like amp curse or shadowfury if you need that sort of utility in a raid fight or M+.
Spec Talents
Like the Warlock class tree the Destro tree build paths are quite similar for all builds. We take the talents we take because it does the most damage in all settings, however, there are a few variations as covered previously with talents; such as soulfire not taken in M+ and demonfire mastery dropped in a raid setting.
Some variations to the builds that I have not included are talents such as Internal combustion in place of reverse entropy. Despite Internal combustion giving a slightly higher DPS output than reverse entropy does in single target, I have opted to not take the talent in the recommended builds. This is because it leads to a very punishing gameplay loop of withers dropping, and generally internal combustion leads to a much more challenging gameplay loop for a small dps gain in relation to reverse entropy.
Fire and Brimstone is taken in the M+ build, however, the point is quite weak, so if you notice low target count pulls in the dungeons you are in, then I would recommend changing fire and brimstone to explosive potential as it allows you to better maintain roaring blaze on the main target of pulls.
With the big buffs to shadowburn in the most recent beta build, it is now the default spender in single target and cleave scenarios. With this change, it gives Destruction Warlock more instant cast abilities and therefore leads to a higher dps output, especially when it comes to having to move around a lot during a raid fight.
Hero Talents
Hellcaller
Wither replaces immolate and is a very strong hero talent in all settings.
Hellcaller also comes with Malevolence, which can be thought of as a mini dark soul; increasing haste by 8% and empowering your active withers. Due to malevolence empowering your active withers it is advised to apply withers to all relevant targets before activating malevolence.
As of the time of writing this, Malevolence is on the global cooldown, leading to a very awkward global where you press it and nothing much really happens.
Diabolist
Diabolic Ritual is quite flavourful to the warlock theme of summoning demons to deal damage for you, however, this hero talent tree is behind the wither gameplay loop as of writing. That being said, it has quite high peaks in large AoE dungeon pulls when your ruination summon lines up with a lot of stacked mobs.