one thing is, a lot of the mystery room characters have no equipment, and in actuality, roll over quite easily(They are a good source of levels early on when you are first starting the postgame grind, which includes getting some reasonable weapons).
Mind you, some of them are occasionally really strong and shouldnt be messed with.
btw, using a balanced team, I was able to get through all the main story aside from the final boss without any grinding(Or item worlding being the required 10). Only named characters I used were Valvatorez and Fenrich, for that matter. Though Fuka was used for throwing people occasionally.
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"First thing that crosses my mind: I didn't get any GameFAQs Karma yesterday." Math Murderer after getting his appendix removed.