Balthier sounds english because he's archadian.

For me by far (and I can't believe no one has mentioned this) the best voice in the game was Cid's. It was just so damn cool. And I quite liked the voices of the Occurians. I liked the diversity of the accents depending on where they are from. It seemed to go like this:
Dalmasca - American
Archadia - English
Bhujerba - Indian
Rozaria - Russian

That's all the ones I can remember. I think thats it tho.

It was the quality of the voice acting that doubled the disappointment of infrequent cut scenes