Rubba dub, dub! Rub that magic lamp and have a long ass, brutual, determined to drag his ass out for a fight until the bring of death and beyond.
After rubbing the lamp it wasn't long before Zell fell, and Selphie mid battle. All the GFs fell before Diablos' mighty gravity area of affect pretty promptly, so I effectively got stuck having to widdle his health down with basic strikes. Blinding him at least limited his ability to spam AoE *and* lunge a fighter to prompt death but didn't really help with the endless stream of gravity strikes. Losing the healer lead to trading draw-cast-cures and sword strikes, after losing the ability to tag team DPS him between cure cycles. A steady flow based on draw-cast-curing my way to survivle between his area of effect spams.
In the end, expecting to lose my head, a quick scan revealed the drowsy beast was down to about 700 HP. Shouting "WHO DARES, WINS!", I rather picked my ass off the floor and went back to buisness--working in as many magic strikes as I could.
For better or worse determination doesn't tend to be my problem in clearing part of a game.