The problem is, even when YOU know fight mechanics, your healers may not. So maybe you know Ifrit Hard Mode for example, he will use Hellfire and then Incinerate one right after the other, followed by an auto attack that CAN kill you if your healers are too focused on healing others up from Hellfire. So what will you do in that situation where you are not getting immediate healing? Hold on for a 1.15x Heal, or use IB to buffer yourself and use Infuriate/Convalescence? Really, when you know your healers will be distracted, you CAN use Convalescence, IB, Infuriate, IB and build up 5 Wrath again all while keeping the healing bonus of Convalescence... So there truly is no reason to pray to God your healers are on point when you can make sure YOU live if you know the mechanics where your Healers don't know how to play with WAR or know the mechanic themselves.