Currently, GLA is the whore of the game, giving away rampart and sentinel to all classes with a slight reduction of ability. WAR has better defenses currently, more potent blocks (parry takes 0-5 dmg from ifrit, block takes 500+) , rampart, sentinel, and vengeance which is a 50% reduct like sent all on its own (and magic with af body!) not to mention access to PUG second wind and feather foot. blood bath and rampage with steel cyclone more than make up for lack of a self cure, it's more like a constant auto regen. also really high hp.

I've personally run into the wolf area for mask of mortal hex and tanked the whole group (albiet in a full party for the bonus and a whm curing me till i got tp) once you get first steel cyclone off you're self sufficient for the rest of the fight.

anyways back to the point. War is a great tank, tanks tons of mobs, the more there are the bigger heal it gets from rampage as well as many mitigation skills and high enough hp to survive hellfire naked.

Here's my suggestion: simply make pld have magic resistance trait. There's nothing physical in the game that can oneshot it's hp, however voice of the dragon from a chimera can oneshot a pld that isn't wearing a double meld hp set. If we give it a base reduction to magic, it'll offset its low hp and make it a viable pick as a main tank again. 10~20% is all it needs to cut off.

With this change, WAR is still a great tank for nearly everything, but PLD can regain it's place in tanking the stronger mobs because it's low hp is no longer a problem.