Well, let's see how far I've gotten:
By now Setzer, Edgar and Celes are all level 99. Practically invincible, but still, the only harsh encounters are: quick instant death spells. -_- And forgotten to cast Life3 in time.
Right now I've already saved at the save point that appears after beating Atma with Edgar (and oh boy, that was mighty easy =D ).
But right after I saved, I encountered one of those Retainer samurai enemies, and when you kill them, they do one last spell: TradeOff. -_- Which is that instant death spell. Meh. Just something for a new reminder.
For the rest, Celes was just in time for beating Scullions, 'cause they cast doom, and it was like, three times an attack of 10.000 damage, right in time before she was about to die. o.o''''
And Setzer just has to take in the irritating damage from the ninja foes.
But so far so good, I guess.