I agree with Balthier being the main character,sometimes even more so than Ashe.
Although the struggle for Dalmasca is always apparent,theres always the big thing about the manufactured nethicite which would be all about Balthier.
And like it was mentioned before,he plays the hero way more than the other characters.
However,when I played the game I took the "no main character" stance because it just felt better making them ALL the main character rather than just picking favorites and sticking with them constantly.