best combo to duel box?

im planing on switching factions in wow an im wondering what people think is the best combo to level with?

i was thinking shammy + pally or maybe warlock/shammy + mage.

pvp or pve?
instance grinding?
questing?
RAF leveling?

see the wiki at the top? click it... look half way down - see the link that says "Classes" ? click it...

btw... check the dictionary for the difference between duel and dual - it might make a difference in what you are trying to do.