I beat the game at level 38 - it was difficult then. At level 45, it was much easier, but that's because I had more mastered abilities and a good system working for me.

Mastering Mimic isn't really worth it, in my opinion. I'd rather have a diverse team of specialized units.

A good way to get AP early is in Bal Basement - use L5 Doom on the Statues there to get 4-8 AP per fight. Not quite as awesome as fighting Movers, but they're quite abundant and much easier to kill.