Vaan/Ashe - Sword, Shields, Heavy Armor. Mostly used as Tanks with an occasional Red Mage ability. High defense, evade, and attack when possible. Used a lot of Decoy, Cure, Protect, and Haste magicks.

Balthier/Basch - Hammer (if I remember correctly, the one that does weird random damage), Heavy Armor. Used as Damage Dealers. Crazy attack and speed. Usually ended Berserking them at the beginning of the battle.

Fran/Penelo - Bow, Robe, Hat, or Dagger, Shield, Robe, Hat respectively. Used as Healers mainly with support abilities in between for whatever was needed. Fran was usually safe from attack with ranged attacks and Penelo had ridiculous Evade from her weapon and shield (don't remember what they were).

Game was a cinch using this setup.