On a side note, to a point made a couple pages back now, there is almost never such a thing as sudden high damage in this game.

Estimating the probability of players screwing up is part of the healer flow chart and can easily be adapted into a full-kit playstyle.

E.g. I ran Expert last night as AST and noticed that one of my two ninja struggled to avoid AoEs. I dealt with this by timing my CS so that I would always be ready to drop it and patch him up if necessary following major AoEs, and I often pre-shielded so that I could mitigate his next mistake. When I knew that a mechanic wasn't followed immediately by another that would hit him, I kept going as planned and just made sure to fluff him before the next mechanic.