Here is the build:
You can either max out siphon life or corpse explosion. I chose siphon life in this video, but I think corpse explosion would probably work better. This is the most DPS I have been able to do with any character since the ranger nerf. Shaman is consistently around 4k-5k, ranger is around 6k, monk is around 8k, Wizard is around 3k, and this necro clip reached 11k.
Here is the damage:
http://www.twitch.tv/goatsgoatsgoatsgoat/c/4431922Gearing: In this video I maxed crit and nearly maxed crit damage but only had 40% cast speed. Cast speed is much less important because much of the damage being done is as a result of being hit while maxing out invoke fear. I am actually wearing quite a bit of mail armor due to the lack of crit and crit dmg stats on caster gear.
The upside: You murder groups fast. Immune to fear. Cast speed is irrelevant. Can wear plate or whatever and be a battle mage.
The downside: You can die really fast. Survivability is linked to howling terror and your siphon life spell which are both on long cooldowns.
Pro tip: stack tons of exp gear and level like crazy. I think i went from level 31 to level 96 in about 20 hours.