(I do not have pld leveled, but it's SIMILAR in use to stoneskin when I played)
I've only played tanks casually in ARR, but if I ever saw a healer die I'd try to stoneskin as a big cast attack was coming out.
Annoying part was stoneskin would often land too late and the attack bypasses it, almost nullifying the reason I used it, clemancy isn't something I'd use every tank hit, but when I know my healer is strained, and I can give them extra wiggle room, I don't see why not if it can save a wipe.