I just look at it this way.
Since people love cookie cutter ranged parties, WAR will forever be the best tank.
IF people decided "Oh hey, let's do some Melee setup's and add challenge to our stuff" you will find that, indeed, PLD is not broken.
Reason's why:
PLD heals others for better hate - You can't heal ranged, they sit too far away.
Divine Veil - A pretty good regen to keep melee in good top form (Love this during Ifrit.)
Rampart - Stronger when it hits more people. Better hate generation.
Defence Down - This does not benefit cookie cutter BLM setups.

When using close range strategies on bosses, PLD is better suited than warrior but since noone does that, warrior is better.

Take off your safety hard hats people and try it out. You'll be surprised.