Doesn't make much sense though. "Haste" making stuff happen faster is logical. Parry making you be able to do more crusader strikes ? illogical.
Just as logical as many other mechanics. Why would more spirit increase the chance for a boomkin to hit? Why does attack power convert to spell power for tankadins? Why do hunter pets gain stats for gear their master is wearing? Why does dodging something reset the cd on AS? There's no logical reason for any of these things. They're simply mechanics for the sake of balance and gameplay.
As for the "hangup" on keeping avoidance stats around, because there's no actual need to get rid of them. There's a reason that different classes and different roles use different gear, a reason why there are plate helms, mail helms, leather helms, cloth helms, strength helms, agility helms, intellect helms, spirit helms, all of that instead of there just being "helms" with "+awesome" that anyone can use and increase their performance of whatever role they have. There's a careful balance between specialization and homogenization. Make loot too specialized and items are desired by too few people and loot becomes frustrating when nobody in the group can use what dropped or when after weeks upon weeks your item has never dropped because of loot table bloat. Make loot too homogenized and it starts to matter less and less what dropped and just becomes a question of "who gets loot this time". That's why there's 3 of each tier token that can only be used by certain classes instead of there just being a "shoulder token" that anyone can use. Because then you wouldn't care that "your" token dropped, it always drops, all that matters is when it's your turn, which gets boring and predictable.
That balance needs to be considered every time they entertain the idea of homogenizing gear. Do they really want ALL plate specs (minus holy pallies) to be after the same items? Or do they want to keep tanks interested in their gear and dps interested in there gear with only a few items (hit/exp/mast) overlapping? Look at cloth, when they did the spirit->hit thing for hybrids they *could* have done the same thing for warlocks and mages and then they wouldn't have to make hit-cloth (or int/hit rings, necks, cloaks, or weapons) anymore, but instead they decided that they wanted there to be dps-cloth, healing-cloth, and then a few items that work for both.
That's why I posted 2 possible paths they could do. If they decide that homogenizing tank and dps gear will be fine, then they'll make haste and crit more useful as established tank stats. Or if they decide they don't want that much homogenization then they'll need to make avoidance stats contribute to active mitigation. I only gave a couple suggestions for how they could do it.