Necromancy isn't underpowered it just isn't a "Solo" spell type. You are meant to couple Necromancy with other skills and abilities.
To admit Necromancy doesn't play well with pure Spellcasters and works FAR more for Warriors and Rogues. Which is odd given that Witch/Warlock is a Geology + Necromancy combo... Yet this thread isn't addressing that aspect.
As well, and I hate to play this card, but we only are at the immediate start of the game... Necromancy hasn't even shown its true colors yet.
For example Witchcraft (which I will always like more then Necromancy!) had flat out the strongest summon and most potent CCs in the entire game. Yet you would never know that by its first 5 spells (Of which... Two were REALLY good).