Most of characters in this game have some sort of use. I find Naoto be the most useless. Her death spells maybe good on normal enemies(if they arn't immune to them), but when it comes to bosses she is horrendous. The only offensive she got against a boss is almighty spell coupled with misplaced mind charged(the only ally with this skill). Almighty spell doesn't pack much of punch compare to elemental counterpart without boost, amp or equipment. High cost of spell doesn't help either. They should of dump that skill to character that can fully utilize that skill such as Teddy, Yosuke or Yukiko.
Also, I find it strange that Kaiji have absurd amount of strength with low magic stats, yet he's coupled with high-end elemental attacks. He got some good physical skills like Primial Force and attack buff, but it's not enough to compensate lackluster physical skill line up. He should at least have a power charge with some passive defensive skills.