You're kidding right?
RDM isnt brought because it has less personal damage, and similar utility to SMN. Raises on DPS is fine because even missing a single GCD to raid someone is a HUGE loss in terms of overall group damage, they are, afterall, one of the 4 "damage dealers" - Tanks meanwhile, do less damage and them missing a GCD isnt going to necessarily mean you wipe to enrage even if gear is tight.
So lets have a look at PLD.
Amazing group utility? Check.
High damage? Check.
A TEN SECOND FULL INVULNERABILITY.
So...They already have some of the highest damage, some of the best group utility, and arguably the best invlun skill on paper (ignoring the cooldown timer for a moment)....And you want to give them a RAISE!?
PLD would become always the one to raise because it would be the most optimal - That'd make PLD not only required to be brought in prog, but also make it terrible to play. We need to encourage people to start playing tank, not alienate those already playing it.