Argh... I went through four stages without a loss and was doing quite well on the boss (Tiamat for me plus friend's Rudra), but I may have gotten little too hasty with using damaging skills - I burst her down right after she became enraged, but as it turned out I fell short 1 or 2 offense skills from stunning her... And her trigger attack really hurt Around 10 % of HP left hurt too xD
Then again I suppose it was a mistake on my part to not level up Defender weapon as much as I did with assault ones... Still looking forward to following days. While hard, it's certainly doable, even for non-whale players imo.
BTW, for those who didn't know (Including me before thinking: Ah what the hell? I probably won't get through it so I may as well experiment ) - while Kamihime's individual burst attacks are single target, the Full Burst deals damage to all enemies on the field (For me it really helped on stage four.)