Originally Posted by
Bixby
It costs more and is a longer cast than Cure II. If the healer's gear is equal to yours, they cover about the same HP. If the tank (either PLD or WAR, doesn't matter, because their eHP is the same) overgears the healer by a noticeable margin, SS might be more mana efficient. Otherwise, Cure II is more mana efficient and more time efficient, so SS is only worth it if you're near full HP and there's nothing more important to do, or a big incoming hit is going to mean you need SS.
There isn't a ton a healer can do to screw things up for the tank outside the obvious: Don't pull threat (overheal, regen right before a pull, etc.), and don't let the tank die. Almost any other mistake you make is going to make things harder for you, not the tank. That might trickle down to a dead tank, but you're in a better position to judge that yourself most of the time.