Without trying to start an argument, but is part of this thread's purpose to discuss whether tank defensive abilities need diversifying at all? It seems like it would be nigh impossible to balance tanks effectively if they differentiate the defensive cooldowns too much, especially when it comes to fights like say, E2S. That fight (at matching ilvl) demands two defensive cooldowns for very similar defensive values per TB, or else one of the tanks just gets smeared and a healer has to cover for them. You already have issues like Vengeance for WAR practically forcing them (slightly exaggerating) to be MT or risk losing out on damage, in a role slot that already only has 2 per boss in your standard 8 man content.

Wouldn't it be easier to make them more diverse in their offensive abilities instead? Being a few hundred DPS behind the meta tank isn't even close to a death sentence, but if your mitigation isn't up to the task your class becomes an extra healer stressor at best and a liability at worst, this reasoning feels like it's a large part of the reason tanks are currently balanced so well. I can swap between all four of them on basically any of the Savage fights, some are more optimal than others on certain fights, and PLD/GNB outshine DRK/WAR on damage by a few hundred DPS right now, but the difference is so little nobody cares what you play as. Despite this, the tanks feel pretty diverse in practice, even if not on paper. GNB is high APM rotation that plays out almost exactly like a DPS's full rotation, they're the OGCD kings of the tank and you feel it during the fight (for better and worse). PLD is as strict a rotation as you can get, which means it's pretty punishing if you mess up, but the actual rotation is a slow and steady pace, and the ability to do BLM levels of on demand movement with your instant cast window is a true feeling of freedom (not to mention the ability to basically solo leveling dungeons once you get Clemency). WAR is the stout and simple basic tank you'd find in most MMOs, but with the added interest in this game of having absolutely massive burst damage. You may not care for the simple playstyle, but it's generally important to have one class that's just a little bit more basic than the others in your MMO. The DPS have SAM, the tanks have WAR, the healers have WHM. That's not to say the skill ceiling isn't as high for these classes as others, but the skill floor is definitely lowered. DRK I have the least experience with and I admit most on this forum seem to consider it the most "problematic" of the tanks, but speaking purely from a balance perspective: there is no shortage. Tanks are balanced well right now, diverse defensives will threaten that unless the dev team designs every boss with all the tanks in mind (never going to happen).