Don't know where you got that from. All itemlvl 666 weapons are 488.9 DPS.
http://wod.wowhead.com/items=2?filte...=666;maxle=666
Here's itemlvl 630, what looks like heroic dungeon loot. All the melee weapons are 350.2 DPS.
http://wod.wowhead.com/items=2?filte...30#items:0-6-2
WF is a flat 20% chance on attack, not a PPM, and it has no cooldown and no attack power bonus in 6.x. Looking at WF alone, daggers will be perfectly equal with maces, fist weapons, and axes. Dagger WF procs will hit for less, but you'll get more of them. Weapon speed doesn't have any impact on WF performance at all.
Of course enhance will still want slow weapons in both hands due to Stormstrike and Lava Lash, and their PPM impact on weapon enchants. Just not because of Windfury any more.