Staff - 9072.48 to 9712.64 = 640.16
Mace- 7826.34 to 8362.15 = 535.81
Dagger- 7816.89 to 8379.95 = 553.61
OH- 1355.5 to 1441 = 85.5
mace/oh = 621.31
dagger/oh = 639.11
The Mace with two upgrades and Off Hand with none = 9717.65
Both the mace and off hand with two upgrades = 9803.15
The off hand enchant makes the MH/OH combo still superior to the staff. In a full BiS, the dagger/off hand is the best. But I think, in a more realistic world, it's just better to get the mace. One because it is much easier to attain and two the dps difference isn't by much. We also still don't know how the legendarys are really going to work or how they are going to progress. It's a possibility that you want the mace since it will be upgraded to something better throughout the expansion.
Drye