Auto battling ultimate from start does seem pretty risky depending on your set up and team atk. I can seem to consistently clear on auto battle, usually winning on the turn my characters would die from the debuff or the turn after where my subs come in and ones not afflicted with it would finish her off. I'll probably just throw Amon in there for the sake of casting the affliction guard.
I can't really see my dark team being able to handle Ragnarok but I guess we'll see later.