Do you use everyone in battles?

[Nebulance]

Here's the problem with Kimahri: he's not in your party during the single best level-grinding spot in the entire game (the Highbridge). So when you hit the Calm Lands, suddenly you have six world-destroyers and one non-specialized guy who's lagging way behind. It basically cripples him for the rest of the game.

Perfect description of the issue.