As for defencive values i would argue that a 2 hander is superior. With the new wep and runeforge you can get 43 def value on your wep alone. And that's superior to any 1h combo if you just look at defence value. As for the parry gib i would not worry wether you dw or use a 2h. Although i dont know what the realistic difference is in amounts of parries you would get, but with the removal of crushing blows and all the short cd's a dk have. Getting parry gibbed is something you can neglect. Personaly i only stack expertice for threat tbh, less parry haste from the boss is just a bonus.
It would be very intresting to see how much dps dw does thoug since i recon holding threat as a dk might become an issue in the next tier raiding.