I agree with Hartman. I must admit that in my current game, I've got three characters in the mid-60s and three in the low-30s, but I think FFXII is certainly akin to FFX in that it's advantageous to have other characters trained up. As you get to change your party once all your characters die it's handy to have some well trained back-ups who can hold their own in a fight or just make sure you can escape well enough.

As for the levels themselves, I think I was around about 33 myself, so you're about the right levels to get through the Stillshrine okay, though I certainly found it to be one of the most challenging dungeons.