Xemnas --> Sorceror
Xigbar --> Sniper
Xaldin --> Dragoon
Saïx --> Berserker
Axel--> Assassin
Demyx --> Dancer
Luxord --> Gambler
Roxas --> Samurai

Creeps and Dusks are simply cannon fodder. Technically, members higher up will have authority over the lesser-ranked members. Treat them like branches of the government; they have orders, but it's all in the family.