If your going to build a mgic nb for pvp your best bet is using resto staff in your off hand for the heals. As for your main hand dual wield is very viable as is destro, i recommend trying both out and seeing which one you prefer. Also atm 2h offers more tooltip damage than both destro and duel wield so that might be worth a try to.
2 handed sword would be better for spell damage though at one point. Much better in fact