I'm playing in Unknown and so far, none boss was really hard at all. I'm trying to solo all bosses in this playtrough, and until now, i'm doing fine. Repair Fonbot's not that hard when the AI works correctly, but when he goes on ''Frontline mode'' where Guy/Luke/Anise die, then it's hard.
I have to agree with this topic, my first time playing this game i actually died like 20 times against it, so i stopped playing, picked up my Chrono Cross and played it until i beat the game, then went back to tales of the abyss, thank god i did cause i would have missed out on one of my favourite rpgs!!