Hey, Sega. Just wanted you to know there's a bit of a cheesey tactic I'm not sure is intentional or not. The giant bird enemies you can fight on the beach near Temple of the Ancients give HUGE xp. I'm talking like, 2-4 levels worth (depending on current level). Considering they only take a couple of minutes to kill, it seems a bit crazy. They are pretty tough to beat, but you can Slow them with Molotovs (edit) and summon Ifrit for Berserk, and take their threat level down quite a bit. I'm fighting them at level ~40ish on disc 1 and getting 2-2.5 levels a fight for less than 5 minutes of work.
EDIT: On top of that, they also give like 16k gil and over 2k AP.