Personally (and I've posted this before), I've always felt like to separate the tanks all 3 should have equal damage and mitigation, but be separated by the utility they bring. Make it so that any composition can clear it, but certain jobs unique utility can be complimentary to the fight, or maybe even have all 3 have some unique contribution to the fight. It'd be min/maxed by world first raiders, but it'd be very small gains in only certain aspects of the fight that would be trivialized by anyone not racing for world clears (even then if it's a small enough difference people might not care at all). Some could argue that this would be homogenization, but you could definitely make the utility pretty unique while still making them all equally beneficial. I dunno, I always thought it was weird that WAR did more DPS - maybe if it had horrible mitigation, but that seems like a really poor trade off for a y'know... tank.