They got rid of the high HP because I feel like they couldn't be bothered to balance it and just decided to give everyone a flat 20% mitigation across the board. Though imo they should do what they did with the healers and divide the tanks into two categories: High HP and flat mitigation, aka ARR PLD Sword Oath, and WAR Defiance.

WAR/DRK (heavy 2h) can be the high hp pool tanks and PLD/GNB (light 1h) can be the flat mitigation. It could also provide synergy with shield healers like what WAR/SCH used to have more of. Im sure no one will complain of getting Defiance+ToB+crit adlos again. It would also buff DRK's TBN in directly due to the larger HP pool.

Though if you really want "identity" among the tanks, pvp is really the closest you can get for newer players who never played ARR/HW or even SB to a lesser extent, before 4.1 when they completely gutted IR.