I think you are missing my point. What I am trying to say is that PLD utility needs to be changed/increased. Right now the only tank utility in the game falls into 3 categories that matter: Personal DPS, Raid DPS buffs, and Raid Mitigation. Nothing outside of those three things matters at all on a raid level. Designing a fight that better suits PLDs "tools" basically means making the fight have physical busters, physical raidwide damage, and trash mobs that make the shield useful. The problem with that is that IT WON'T MATTER. People will still bring WAR for the increased DPS, Path, and the fact that they mitigate physical moves just as well as magical moves. People will still bring a DrK because guess what, it does more DPS, can survive everything in an encounter, and has utility with Reprisal and Delirium Blade.
The core problem with PLD is that nobody gives a shit about how much a tank can mitigate. It is literally a non-issue. This is due to the tank meta revolving around scripted burst damage, weak AAs, defensive stats being alonst worthless, and what utility a tank brings to the table.
So once again we need look at the three things that MATTER: Personal DPS, Raid DPS increases, and Raid Mitigation.
The only area that makes sense for PLD to be buffed is in Raid DPS incease (Think Ninja). This would go a long way in alleviating the tanking problems. Particularly the PLD+Drk party composition problems.
If you make PLD the Raid Wide DPS buff + High personal mitigation + Low Personal DPS tank and DrK the Raid Wide Damage Taken Debuff tank with moderate personal DPS then there would be some incentive to run DrK+PLD.
The problem that we will continue to see with the 3 tank system is that parties will generally be taking whichever composition allows for the most DPS.
So until we see the day when WAR+PLD, WAR+DRK, and PLD+DRK all equal comparable raid DPS; one tank will continue to be left out.