If you check out the list of races and templates for my campaign, you won't see Necromancers from DF 9.
Yet we have Gerry the Necromancer adventuring around the Cold Fens and the Lost City.
I have some basic guidelines to determine who is a "necromancer."
10+ points in Necromany spells: Access to Necromancer power-ups, access to Foul Arms (DF 11 and Pyramid 3/01), and Necromancer perks (Lesser Lichdom, etc.)
10+ points in Necromancy spells including Zombie: Access to Ally Groups of skeletons or zombies. Can make their own Foul Arms.
20+ points in Necromancy spells: Any appropriate advantages from the Necromancer template (DF 9).
We don't use the Necromancy Power Modifier; instead, any powers gained depend on Magery.
I don't use Deathliness (since they have Magery anyway), so it's really just a question of providing a basis. I don't really want to just open the door so you have fire-wizards and illusion-wizards and so on buying Foul Arms and Lesser Lichdom and a squad of zombies. At the same time, I feel like as cool as the Necromancer template is, it's better off in my game as a lens on wizards.
We've expanded the Necromancer spell list a little, too. While I don't let PCs develop their own spells (it's a game of discovery and looting, not between-session research) I do take suggestions for new spells from players. And Gerry's player has suggested some pretty excellent ones. Those might be out in forgotten tomes (and tombs), etched into sarcophagus lids, written on mummy wrappings, and scratched into the flesh of undead beasts.