I would just like to point out that PLD is not better overall at mitigation than a WAR and that in a lot of instances, such as boss fights, a WAR can have better mitigation.
This is because of a few things.
First off the eHP provided by the two tank stances is the same.
Rampart and Inner Beast. While IB has a shorter uptime, it can be used more frequently as long as you are doing your rotations which results in approximately the same overall uptime for the two. The differences: IB does damage and has a self heal, but the big one is that they actually don't mitigate the same % amount because of ShO being a base % damage reduction which means Rampart actually ends up being a 16% damage reduction while IB is still 20%. When coupled with the tank stance buffs, their defensive gain is the same. Also, as far as the difficulty of timing IB to big attacks, Infuriate + IB is available more often than Rampart so while you have to push one more button you can time it to more potential big attacks.
Sentinel and Vengeance. Sentinel with the trait says it does 40% damage reduction which actually results in a 32% damage reduction and lasts for 10 seconds and is on a CD timer of 180s. Vengeance does 30% damage reduction, does damage on being hit by physical attacks, lasts for 15s and has a 120s CD timer. When coupled with the tank stance benefits, they result in approximately the same defensive gains. Sentinel will provide a bit more mitigation per hit over a shorter period of time, while Vengeance lasts longer but has less mitigation per hit. However there still is the discrepancy of the cooldown times between the two (180s vs. 120s) and that Vengeance also does damage.
Bulwark and Foresight. This one is a bit harder to measure because of block. Bulwark can give greater burst damage reduction, but it has a shorter duration and longer cool down. Foresight may do less reduction but it lasts longer and can be used more often. The difficult to compare elements are that block could potentially block a really nasty attack or hit, but then again it probably won't. The chance of that happening is quite low so you should never plan around it.
Holmgang and Hallowed Ground. HG is better IMO and Holmgang could use some rework/a buff.
Thrill of Battle and Stoneskin. They function pretty much the same, the main differences being SS has a cast time but no cooldown and ToB does not have a cast time but has a cool down, ToB can stack with a SS cast by a healer. Also, with the trait ToB does 20% instead of 10%.
Convalescence. Same ability for both, but the PLD version is better due to trait.
Bloodbath. Same ability for both, but WAR version is slightly better due to trait.
Awareness. Pretty meh for either class.
Rage of Halone debuff and Storm's Path debuff. SP's damage reduced debuff is better than RoH's strength debuff since it affects all damage.
Block and Self-heals. Different flavor elements for both classes. While people like to say that the shield is a huge deal, it only works on physical attacks so is mainly effective for negating an auto attack here and there unless you use Bulwark but that ability should be looked at separately. So in most instances, they result in approximately the same amount of mitigation.
While it may seem like I am showing that WAR mitigation is better, it really depends on the situation. In boss fights and magic heavy fights, WAR can have better mitigation. In large trash pulls or physical damage heavy fights, PLD may have better mitigation.
Point being this whole PLD is defensive and WAR is offensive so should do much higher damage is only true conceptually and not functionally, so justifying the much greater amount of damage that a WAR can do solo or MTing is moot since their mitigation does not have this sort of discrepancy.
Also as I was suggesting, any buffs to PLD damage would be limited to only while using shield oath since that is where the big damage difference is, when both tanks are in their tank stance.