WoW Classic – Is Annihilator Worth Using?
While the proc rate of Annihilator is very low and the proc itself has a chance to be resisted, a single lucky application of the debuff is a 4-5% damage increase for every physical damage dealer in the raid. It is up to each guild to decide if the potential damage gain, multiplied by the amount of melees in the raid composition, is worth sacrificing a bit of damage on the off-tanks for a chance to proc Annihilator. It is unreliable and definitely not an engaging role for your off-tanks, fishing for procs all encounters, so you should discuss this decision as a guild.
A more reliable way to get rid of the remaining armor on the boss is to use Improved Expose Armor, but this method comes with a severe drawback: your tanks won’t be able to use Sunder Armor for threat and will have to dump rage using Heroic Strike and Battle Shout only. Obviously this is less of a concern for alliance tanks since Salvation gives a lot of room for threat. Discuss it with your guild and your tanks, try it and see if it works out for you.