If your going enhance and duel wielding, make sure to have 2 SLOW weapons (2.6+ pref) the slower the better. Slap windfury on both and your set.

Edit: Might as well explain why.

Somewhere along the road windfury got nerfed, putting a hidden 3 second cooldown on the proc (Windfury can only proc once every 3 seconds) so if you have a fast offhand, its just going to eat up your windfurys that COULD be proccing off the mainhand. Therefor you want weapon speeds to be as close to 3 seconds as you can.

About the fast off-hand, if you have any fast offhand weapon, you can just use rockbiter, flametongue or frostbrand on it. So which will result in only windfury procs of your main hand :).

When the patch went out for the windfury "hidden" 3 sec cooldown I just had my main-hand use windfury (Reflex blades with 2.70 speed) and my off hand with frostnova (Stormweaver warblades with 1.60 speed) the reason is want to slow down my enemy because gives me a higher chance to unload my windfury on them (you only have a 20% chance). So I ask you would you rather slow down you enemy so you have a better chance of hitting that 20%? if you think duel wielding 2 slow weapons is the way to go then you might as well carry a big slow two-handed weapon and forget putting talent points in duel wield.

Remember this combo: Stormstrike, one of your shock spells, turn his face into jelly and then another shock spell. Rinse and repeat