Necromancers are already the most versatile class there is. :-)
You can make several good builds using any of the three skill chains.

Death Magic gives you minions, self healing, and some decent damage dealing spells.
Blood Magic is good for support, damage, self healing, and AoE healing.
Curses is good for ****ing off the enemy with degeneration, and Spiteful Spirit.
And they get fairly good energy management via Soul Reaping.