The DPS for necromancers is most certainly not the issue
Survivability comes from DS naturally, if you get to understand the boss mechanics better, you know when to pop it (say Archdiver or Mossman in Fractals)...
Rotation in DS is pretty much 5, and then 4 times #1
I just put this together and took it for a test run in the LA event. My god, this is so damn fun, I love the challenge you face trying to maintain melee range and having to know when to bounce between each weapon set. I find that using axe and focus is definitely preferable when you're out roaming in open world, but for self contained instances such as dungeons and bosses, dagger warhorn works quite admirably.
You're literally dancing between death shroud and stabbing people in the face. I'm not completely geared out yet, but I can definitely see the appeal. Still, I'm worried about how viable the range thing is in fractals, especially when you're against something like dredge and you have to fight the ice elemental or mining suit where even death shrouds shadow bolt seems too short of range.
I'll have to play around with this a bit more to see how I do with the build, but so far, despite it not being the best DPS class in the game, it satisfies my desire for an extremely technical and downright hectic play style (Which is why I love all the light armor classes)