Basically, I Darkness stuff on the pull, and then beat the living crap out of it when it gets to me.
If it starts being annoying, Fear it (keeping Darkness up) and continue beating the living crap out of it.
If it starts being super annoying, HT it, and continue you-know-what.
Undead are awesome because of Spook the Dead.
If it isn't crowded, use your pet as an additional DoT, but I often skip the pet because he pulls aggro from trash with his greenness.
For tougher mobs, throw on yet another DoT (in addition to Darkness), like Heat Blood.
Siphon Strength every few pulls since it's practically free and gives you a little more melee dmg.
And hope for a patch soon so that Fear/Spook the Dead is fixed.
And mana shouldn't be an issue, and Blood Ember items take forever to cast...I would only get BE stuff for the AC or some handy utilities (like Gather Shadows on the BE Bracer).