Late to the party I suppose, but Kanno's right on, levels aren't that important in the game, especially on the final boss where mastering job classes becomes more important for stat bonuses. I beat the game for the first time with my highest levels being 38 (just this morning actually) and though I ran into some minor difficulties it was more because powerful attacks surprised me, not because it was actually difficult. Even beat it on the first try so it's not that hard.