The answer to Mages, actually, is having them use their Rods as items. Go into Items menu in battle, hit up on the D-pad, double-tap A to select usign it as an item, and select the enemy you want to hit. Free fire/ice/lightning/mage arrows/whatever spells, ad infinitum; only drawback is single-target.

FF4 icons: antigonist is where I got most of mine. Hers are beautiful.

What level are you, roughly, for the Baron battle? And is it [spoiler throne room boss] or [spoiler castle hallway boss] who's causing you trouble?