Frostling: I never much liked them as necromancers, but the frost/fire damage on witches/whatever unit they buff can be nice, and if you can push out an early deathbringer (so, before late game) their units are very good for promoting ghouling. Orcs: Throw curse on reanimators, bonus health offsets Ghoul minus, very high physical damage (what I find necro most often lacks).

Elves: Lightning helps vs enemy undead, though you lose the total immunity to blight. Blight doctors don't do enough to offset this.

Pop bonus to help offset necromancer's slower growthĭisadvantages lie in fragility (you almost always want embalmers guild) and effectiveness vs undead: necro is already bad at dealing with other undead, and making a ton of your units blight focused doens't help. Inflict Weakened at max racial governance. Also, swarms combine well with Bone collector and Corpus Furia your front ranks may well fall, but your followup will crush your opponent. You're already in the swarm mentality, keep with it. High rank blight doctors inflict huge morale penalties, works well with lost souls, and as Anime pointed out, they get Heal Undead pretty fast. Use untouchables as expendable units, raise them as cadavers if they die. Lesser reanimate on swarm darters/untouchables (which I usually spam)

Tigran warlord age of wonders 3