...I COULD GO ON ALL DAY.
So could I! Time for a nerd out!
Dias's killer moves are terrible but since he can wield a Levantine, he's fine (Levantine + Angel Armband)
Anyone who can wield a Levantine + Angel Armband should just use normal attacks anyway (Claude & Ashton)
Chisato is special in the sense that she has a naturally high enough AGI that you can make her a dodger only. You can start her with a Mithril Dress + Jeanne shield and later go Valkyrie Garb + Star Shield. At level 255 with the prior items even Iseria Queen has a hard time hitting her. The Weird Slayer will also heal her whenever something does manage to hit her.
Bowman should only be used as a Poison Pill (and later Explosion Pill) tosser. All his other move are terrible and his normal attacks will never connect because of his 1 mm range. While it may sound bad, Poison Pill and Explosion Pill become REALLY strong with use.
Leon and Celine are both terrible later in the game but Leon is slightly better due to the Gremlin spell which is non-elemental and does multiple hits.
Ernest is bad... no saving grace. The only good thing about him is that you can steal 2 Battle Suits off him.
Noel has Earthquake and that's about it.