I don't know whether or not you are over-leveled, but it is too easy to over-level in general in FFX. With optional "super-bosses" in the monster arena that would laugh at the final boss of the game, the ability for any character to level more than what's required is too easy. I find that I can hang out for a couple of hours at the first forest in the game where you find the Lord Ocho or whatever.

FYI, I don't know if you know or not, but there are spoiler tags([SPOILER][/SPOILER]) that make the text (SPOILER)look like this.