DRK shoulda been built around taking up blood in place of HP as a resource, while under dark side. (due to the abusive nature of this, since tanks barely need healing, all -hp/blood effects do more dmg if blood is the resource spent.)
(Also DRK should have had super bolide. Sacrifice all HP to become invincible. Throw up TBN right before, so u dont die to server tick at 1hp.)
In place of their pet on a long cool down, it should be a "death Grip/pull" that works on bosses, to cheese mechanics. But since its a DPS loss, the cheese better be worth it.
(Still put on a long CD, so it cant be spammed)
WAR is essentially "Barbarian" to the japanese, its not based on the FF1 Warrior/Fighter job (PLD is based on those jobs) its mostly based on the FF5 Berserker, along with FF11s.
Berserk isnt a very good mechanic in an MMO, so in this game, it makes u go "nuts" spamming the same ability.
But it looses that "uniqueness" when DRK has a semi clone of it.
Instead, Berserk should be what happens when you reach maximum gauge. But to maximize its potential, you want to time it with Inner Release (for the same effect we currently have)
You try to keep your "rage" as high as possible, while spending some in fell cleaves, so as not to max out. (keeping it higher should raise dmg in some way, most likely increase fell cleave dmg)
Also WAR should have had "Living Dead" but instead, it gets a true berserk status if they arent healed to full, to calm them down. (When true berserked, they spam attacks randomly, and you dont get to choose which skills. Leading to a huge DPS loss.) They can also self heal to help cover the missing HP.
GNB (A lot is wrong here, but Im not going to bother with this one.)
Only statement being it should have had holmgang.
PLD seems mostly fine, but its gauge really does feel tacked on. Considering it uses MP, it doesnt need a gauge at all. When everyone has a guage, the concept of a gauge feels like its no longer interesting/special.
So I simply say, get rid of it on PLD. This helps add some identity between the tanks.