You know there was an old article in Dragon a ways back called "More Bang for your Bones" which went into the subject matter.
I'll take a bit of advise from that article here: Let him have stronger corpses to work with (or failing that have someone Transmute the body of a corpse into another thing). For example at 25 HD he can have a small army of weak skeletons or a Red Wyrm Dragon (HD 25) skeleton.
A 'black' necromancer follows the ideal "Waste Not, Want Not" while other Players may have interest in finding the brutally killed body of a random dragon, a Necromancer sees possibility.
Of course this might imbalance in a different way, but there are reasons for Necromancer being feared... and it aint Cause Fear.