I always had Balthier as my party leader. But... He had a gun, nothing else. Was a mediocre spellcaster and a slow attacker. He is now in my reserves.
Vaan is my party leader now, he is also my tank, the party leader always has the front. Looks like a win-win situation to me. He is always accompanied by Basch and Ashe, as dps and healer.
The battle system is really good, as long as you ditch those annoying gambits. Gives a better feel to it, harder and more fun.