PLD is already the only one who can take any tankbuster without any assistance. The only one who could eat a chain of Akh Morn without someone to keep it alive...
Again, when you're in a Duty, your goal is to win. A situation where you screw everything and still recover is hardly significant enough to dismiss an option. When you give PLD an ability so important that it becomes your main strat, then, yes, you could say that is brings balance issue.
You mean the orb part ? Where healers can save everyone by Stonekin, Succor, Sacred Soil, etc ? So, do you suggest we remove Cover because a PLD could use it to prevent one healer fom dying and allowing him to cast the LB3 ?
So, you mean that you don't want PLD to be able to heal because it would steal you whole role ? Are you, again, reducing healers at spamming Cure so that you fear being oveshadowed by a PLD ?
I don't even have a healer at lvl 60, yet I know exactly that they can offer more than that.