Well I know Dario ain't tough in new game +. However, I just had heck of a time the first time around. First all I had were the crap white healing spells. No holy heals(or maybe I had one.. don't remember), or real strong white elements. That and Dario hit her first... she didn't survive. I had one revive. So I said screw it and just left her dead. Fargo and Serge took him out. The blue (cure all(or whatever the best blue cure is)) was powerful enough to handle anything Dario could throw. And invincible really hurts at times.

Anyways... I just don't like having to have riddle. I find her to be generally useless. Afterall my Fargo with the blue specific heal could easily fully heal the entire party at the end of the game. And he hits harder with physical, and can hit fairly hard with techs(invincible, strength, eagle eye, etc).