PLD is supposed to be an "iron fortress" type of job; it is supposed to be a job that can tank a lot of damage while being unable to deal a lot of damage. I think thematically it only makes sense for PLD's damage to be the lowest out of all the tanks, and every buff given to PLD dps only serves to distance it from that theme. I think that instead of increasing PLD's personal dps, Square Enix should nerf PLD's damage while giving it utility that increases the damage of other party members. There are probably a lot of ways to do this, but of course balancing will always be an issue. In any case, with such changes, the PLD would deal poop damage as it should, but raid groups would still want a PLD in the team because bringing a PLD into the team doesn't equal a loss in raidwide dps compared to WARs or DRKs.
Edit: DRKs and WARs are currently in a good spot IMO. It's PLD that needs some love. DRK doesn't need any more damage. Grit having a huge MP cost is actually a fun mechanic for DRK. You have to make sure you're not just absentmindedly stance dancing due to the huge mp cost. This encourages DRK players to think and plan more. Having a recast timer shared with Blood Weapon limits control over stance dancing. What if I wanted to drop Grit but NOT use Blood Weapon yet because I want the extra mp I'd gain if I could use Low Blow and Plunge during Blood Weapon? I'd have to wait a few seconds so that Low Blow and Plunge would land in my Blood Weapon window. Living Dead is fine as it is -- only noob groups or pugs can't make full use of it which makes it extremely satisfying when you do have a group who can use it to their advantage. WAR tankiness is in a good spot right now, so that 15% damage reduction is indeed too OP. The "Enraged" mechanic for a WAR provoke is interesting and would push the WAR more into the OT role, but I will not comment on its validity xD. Interesting nonetheless.