Just to lob this in, as I read about the 2h weapon being involved in the decision-making process... You may also want to consider the "ShadowFrost" build (I think I have the name right, but it's been a while I admit; and, I am not sure how it compares to standard Unholy/Frost Dual Wield. I forget the specifics but it's mainly a Frost-tree spec with some points splashed into Blood and Unholy, with your DPS being done in
Unholy presence. I've never tried it myself, but I recall EJ having some mention of it. I'll toss a link to it here ->
Shadowfrost 2.0
Not sure if it helps, but it's something else to consider. Hope whatever you decide works out for you.