Yeah, I try to rotate my characters but I still end up with a big experience gap between the player and the party (which is okay). I also still end up with a gap among the party simply because some characters aren't as effective as others in a given situation. Like, I enjoyed Apolishimo and tried to use him but he'd always fall behind by the end of the game because he doesn't work well for full-on offensive parties or fights against all of the creatures that resist his skills. I'd like some kind of mechanism to keep them from falling too far behind without having to significantly cripple my fighting power just to grind up their exp.
These days I lean more to just using the characters I like most. Like kadakithis, I enjoy building my party around what would match the story, even if it might be sub-optimal tactically.