Haste > Mastery > Crit > Versatility > Agility
Haste: This is your best stat in single target fights. It increases your energy regeneration and attack speed. Energy regeneration is essential in single target fights where you don’t have multiple bleeds running, it helps with Double Dose stacks and generally maintaining your Envenom, Elaborate Planning buffs.
Mastery: Increases your poison and bleed damage. It’s already a great stat for ST and it becomes a whole lot better when it comes to cleave since most of your damage comes from your Garrote and Rupture, particularly when you’re running Shrouded Suffocation and/or Subterfuge.
Versatility: This increases the damage that you deal and reduces the damage that you take. It’s a pretty straight forward stat that sees no overwhelming benefit from stacking it. However, you can see some benefit from the damage reduction you get in case you have to soak a mechanic.
Critical Strike: Crit is essential for Assassination because of Seal Fate. Your Mutilate critting helps a lot with the fluidity of the spec and maintaining its buffs. It’s especially good when you get good RNG, during your Toxic Blade window which helps with pumping the 3x Envenom during that.
Generally you should be simming to find out your best stats. But in BoD with our current traits and most fights being so single target dependent, going for Haste > Mastery is a very safe bet, with Crit being just slightly behind those two.
The best way to calculate stat priorities for your character is to "sim" your characterFind out how to sim
Rings: Pact of Haste
Gems: Quick Owlseye
Potion: Battle Potion of Agility
Flask: Flask of the Currents