I just played through IV (for psp) using just Edward (for the VERY brief window he is available plus endgame). For the first part it actually gave me perspective as to what they were thinking when they designed the mechanics of the character. As soon as you get the Lamia harp he becomes amazing. Everything gets confused except Mom Bomb and Antlion, and even they weren't hard because the damage he received in the back row was easy enough to deal with using potions. In a regular game you never really appreciate him because you're brute forcing everything with Cecil and then Cecil AND Yang so he just seems like pointless chip damage, but if you let him do his thing hes a very satisfying party member.