Originally Posted by
Shiira
Every single auto attack gives ret paladins three chances to gain a stack and every single melee ability gives them two. When they hit eight stacks and the proc goes off it will also proc their seal, which can crit for several thousand damage. Deathbringers will isn't great for ret so they don't have many options.
For rogues the trinket is able to proc poisons. That doesn't do as much damage as the seals from a ret paladin but they gain stacks faster so it's still worth it. Rogues would only use deathbringers will as combat and have crit capping issues, this leaves mutilate with tiny abom and war token as their only options anyway.
Shamans also gain stacks very quickly because of the amount of haste they usually have, and the proc can give them stacks of maelstrom weapon. They also have crit happing issues and don't want armour penetration, so they also don't have many options available to them.
When a frost dk procs the trinket all that happens is an instant for a couple of thousand damage. It doesn't proc necrosis or blood caked blade and there are no other mechanics that make the proc good. The hit isn't particularly useful either. Dks also have more options for trinkets than any of the classes I mentioned because while some stats are better than others none of them are terrible.
From a raid leading perspective there is no reason to give the trinket to a dk. It's bis for ret, mutilate and enhancement. I'm not sure about combat but it can't be far off. A dk would replace it as soon as anything as soon as normal deaths choice or anything better drops, the other classes would not. I'm saying this as a dk, the trinket is potentially an upgrade if your current trinkets are horribly outdated but it will almost never be a bigger raid dps increaase to give it to a dk than the specs that it's actually good for.