Lightning - Red Mage: Good at attack, good at magic, but not strongest in either areas compared to the rest of her party. Still it's probably what she'll spend all her time doing, so yeah.
Sazh - Bard: Does he sing songs? Well, not that I've seen. Does he use an instrument? Well, not really. But he's great at buffing, debuffing and long range attacks. To me, this reads "Bard" all over.
Snow - Monk: Uses his fists and has so much health he doesn't know what to do with it.
Hope & Vanille: Both are equally black mage and white mage. If I had to pick which is which, I would have Vanille as the Black Mage because her special attack is Death, and there is no way in hell a White Mage would ever have that. Meanwhile, Hope's summon is Alexander who uses Holy, which is White Magic.
Fang - Dragoon: I think everyone can agree on this, it's pretty obvious.