The Tavern

whooaa, in 0.21 this school is extremely overpowered.

Infestation: don't let this affect invisible area, and don't let insubstantial/nonliving enemies be affected

Vile Clutch: another OP spell. 3x3 smiting is went too far and the damage output is too strong.
also zombie hands catching flying mobs is absurd. should be nerfed

Regeneration: Remove

Alternative proposal: Split Necromancy in two, like Enchantments. Both schools had too many good things in them.

Necromancy (corpses): Animate Skeleton, Corpse Rot, Sublimation of Blood (dual school), Animate Dead, Dispel Undead, Cigotuvi's Embrace, Death Channel, Simulacrum, Haunt, Cigotuvi's Vile Clutch, Infestation

Necromancy (life): Pain, Sublimation of Blood (dual school), Regeneration, Vampiric Draining, Agony, Bolt of Draining, Excruciating Wounds, Borgnjor's Revivification, Death's Door, Necromutation

These are a bit on the small side, but additional spells can be developed to flesh them out, like Charms and Hexes were. Good gods can hate both of them, but since good gods aren't appreciably stronger than other choices and don't need this drawback, this is also an opportunity to remove that rule.

Also needs bikeshedding for names, I guess?

Not that I think the school needs split necessarily, but I could suggest:

Fleshcrafting and Lifebinding

As school names, both still have a somewhat "evil" sound to them to me.

Creating yet another spell school and then adding even more spells seems unrealistic to me. If the problem is that necromancy provides too much utility compared to other schools for the same investment (I think this is probably true) and you don't want to nerf or remove any spells, you can just move spells out of necromancy and into some other school. Agony is basically a hex, zombie hands could easily be reflavored to fit earth/anything else (sorry Mikee_), one of revivification/ddoor could move to poison magic since the devs insist on keeping it around, etc. That's a lot less work than adding a whole additional school.

I am also puzzled by the selection of "overpowered" spells in the op. When I think of overpowered necromancy spells, I think of corpse rot and the two animate spells. Infestation is certainly less powerful than revivification or death's door and is a questionable investment in a 3 rune game. Not letting it affect areas out of los seems reasonable though. Zombie hands is good and usually mp efficient by direct damage spell standards but is far less absurd than the extra damage you get from killing a couple guys and casting animate dead once. Regen is tedious and annoying to use and such low investment that you always want to get it for out of combat use, but in terms of making your character better at fighting stuff it is massively overrated outside of abyss/extended/orbrun.

When I think OP necromancy spells I think necromutation and regeneration....

Though I haven't seen the new spells yet.

The only OP necromancy spells are probably regeneration and animate dead. Possibly vamp draining, but few people use that anyways unless they're trying to heal a DD. And it's range 1 anyways, so I suppose it compensates for that with good power.

I avoid allies so I don't use animate dead often, and while I do think regeneration is very strong, it's also pretty crucial to extended, so I wouldn't want it removed. You could always bump it up to level 4 and that'd probably be quite fair.

I haven't used clutch enough to really be sure, it does seem strong, but it's also a level 5 dual school spell, which should be pretty strong. (Most) Bolts are a level higher, but those are strong enough to clear the whole game, so clutch clearing the midgame well isn't really a problem in itself.

That's true, but it seems to me that necromancy has two coherent themes ("spells that interact with corpses/undead" and "spells that interact with your HP, plus the odd direct damage effects"), with both of these categories being flexible enough to support their own schools. That was my reasoning behind the suggestion for a split.

I'd be all for some Necromancy spells moving to Poison, though.

All Necromancy spells:
Agony
Animate Dead
Animate Skeleton
Black Mark
Bind Souls
Bolt of Draining
Borgnjor's Revivification
Borgnjor's Vile Clutch
Brain Feed
Call Lost Soul
Control Undead
Corpse Rot
Death Channel
Death Rattle
Death's Door
Dispel Undead
Drain Life
Excruciating Wounds
Flay
Ghostly Fireball
Ghostly Sacrifice
Haunt
Heal Other
Infestation
Major Healing
Malign Offering
Minor Healing
Necromutation
Pain
Regeneration
Simulacrum
Spectral Cloud
Sublimation of Blood
Summon Drakes
Summon Scarabs
Summon Spectral Orcs
Summon Undead
Symbol of Torment
Vampiric Draining
Twisted Resurrection

The ones that create undead or inflict draining need to stay as Necromancy so that, if nothing else, it's easily identifiable that good gods hate them.
Most of the damage spells are resisted with rN, so if you move them to another school, you should also change their damage types. Flay and Borgnjor's Vile Clutch are exceptions that would only require flavour changes, but moving Flay doesn't strike me as useful since the monster that uses it is undead anyway.

I think the healing spells should be moved out of Necromancy (Charms would be an appropriate destination) since they currently use an extra spell flag to mark them as "not evil, even though it's necromancy". If you want them to not be evil then just put them in a school that isn't Necromancy!

The suggested split results in these schools:
Damage and HP school: Agony, Black Mark, Bolt of Draining, Borgnjor's Revivification, Borgnjor's Vile Clutch, Death Rattle, Death's Door, Drain Life, Excruciating Wounds, Flay, Ghostly Fireball, Ghostly Sacrifice, Heal Other, Major Healing, Malign Offering, Minor Healing, Pain, Regeneration, Sublimation of Blood, Symbol of Torment, Vampiric Draining.
Corpse and undead school: Animate Dead, Animate Skeleton, Bind Souls, Call Lost Soul, Control Undead, Corpse Rot, Death Channel, Haunt, Infestation, Necromutation, Simulacrum, Summon Scarabs, Summon Spectral Orcs, Summon Undead, Twisted Resurrection
Spells that fit in both: Dispel Undead, Spectral Cloud
Spells that don't fit in either: Brain Feed, Summon Drakes

Overall, the schools are about the same size; 10 player-castable spells in the damage and HP school versus 9 in the other one. However, the corpse and undead school is redundant with Summoning, having only two spells that don't create allies, and one of them is the bad joke that is Necromutation.
I'm not sure making allies out of hostile monsters and corpses is a good enough feature to be worth its own spell school, when there's already another spell school dedicated to making allies. I would be interested in getting rid of corpse interaction altogether.

Another possible angle is moving Borgnjor's Revivification, Death's Door, and Regeneration to pure Charms. Death's Door is already the only useful Charms spell above level 5 (I'm not counting Deflect Missiles as a real level 6 spell because its success rate doesn't matter so it acts more like level 3).

An option would be to leave necromancy as "blast necromancer" and give all undead-raising spells to Kiku or Yred. Maybe make undead servants really Kiku's exclusive thing. (I consider clutch a non-undead spell).

BTW, a revision of how necromancy interacts with corpses could also be a step towards removing screen clutter like uneatable corpses and noxious chunks, or even towards removing butchering altogether.