I bet you Blizzard hasn't even thought of putting in a dueling system. *eyeroll*
It's clear to me that the classes are extremely unbalanced in PvP right now, so rather than spend the next year balancing, they are releasing the game, and introducing PvP later.
Solution? Spend the next year(after May 15th) petitioning the new forums for open world PvP. But you can't really be so naive as to think Blizzard never thought about PvP dueling in open world.