How important do you rate weapon damage for Protection?
Reason I am wondering about the value of weapon DPS is because I've currently got a heroic warforged version of Xifeng (http://www.wowhead.com/item=105460) and a regular heroic version of Encapsulated Essence (http://www.wowhead.com/item=104421). Besides the obviously better stats on the mace, I'd go way over the hitcap with Xifeng (almost 2% over). The only way to compensate for this would be to drop the 2-set bonus in favour of off-pieces with no hit rating on it like the tier legs do.
I'm personally leaning towards 2-set with mace, the extra parry might make up for the loss in weapon damage. Not to mention the set bonus for survivability. DPS is a concern for me though, I don't want to sacrifice lots of it for a slight gain in survivability.
With the high Vengeance levels most dmg comes from attackpower while tanking. Weapon Dmg is only a minor factor for Tank-Dps.
This means you should take the weapon with the better secondary stats in this case - since weapon dmg difference is minimal anyways.
Weapon dps is pretty much meaningless for prot warrior/pally (only about 20-30% of damage done by weapon skills) and since you can't utilize any of the hit the answer should be clear.
The stat distribution on the sword is kind of bad as well since even if you had low enough hit to reforge off the mastery you wouldn't gain much.