I think the best duo would be...A Warrior and...

another Warrior.

On a more serious note I think a SMN/RDM would be interesting. Two DPS, both ranged so you can pull from a safe hallway so you don't activate traps until the room is pretty much safe, One can somewhat heal? Maybe? Forgot when Vercure was. Regardless sustaining potions can serve both well. Also both can raise? Not sure if RDM has it yet but if not at least one can.