Necromancy damage is increased by:
Intelligence
Warfare (physical damage)
Necromancy is an unusual group of spells in that they are cast much like other magic and that are also Int based but they get bonuses from Warfare instead of their own school. It keeps things interesting.
OPINION: Necromancy is not that strong as a primary school but is great to "splash" into other setups. Death wish is useful for anyone as is the incredibly overpowered Living on the Edge. A couple points of Necromancy also help you heal off HP damage you deliver regardless of what skills you are using. My physical characters always have a little necro to keep their hit points capped.
STRATEGY SUGGESTION: Use Death Wish along side What a Rush on a high wits/initiative character. Have allies bring you down to low health before entering combat. Initiate combat and enjoy huge damage bonuses with additional AP - hurt the enemies enough heal all your hit points due to the points in necromancy.
