Naoto's lousy at boss fights, yes, but he makes dungeon crawling a breeeeeeeeze. I tossed him the Chakra Ring, and combined with Relaxing Wave, he's usually able to kill everything and end up with very little, if any, SP gone at the end of the battle. He's got a constant spot in my party for dungeon crawling. Especially the dungeons with Gold Hands that have ridiculously large amounts of HP. Hamaon + Hama Boost = 18k yen for 7 SP, and it's missed ONCE out of maybe 10 hands. Might just be me, but Light/Dark magic seems far more useful in P4 compared to 3.
What I meant in my conjecture concerning Kanji was that I almost always choose my party members for specific purposes, meaning that he's in direct competition with the MC most of the time. The other characters can at least deal fairly respectable damage with their elemental spells. Kaji was hitting for single-digits against enemies weak to his element, and he certainly wasn't underleveled at the time. Eh...I dunno. Kanji. Meh.
He's still awesome characterwise, though!