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Would it work well to have an army without vampires? Maybe having 2 Necros, 1 Wraith and 1 Wight as leaderS?
I would doubt it. It's legal and all, but an army lacking the powerful combat abilities of a vampire will need to make up for it in magic. Only two necros will have a hard time accomplishing that.
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I think you can pull it off, but it's just harder to win consistently.
I'd take a master necro and a lvl 2 necro. I'd give the lvl 2 guy a power familiar so that he had three power dice all his own and the master necro could use six power dice for his spells (probably using three each time).
Then I'd give the master the obsidian amulet and the cloak of mist and shadows. So that means no BoA or SoD.
For killing power, I'd take two wight lords. One mounted with Sword of Kings and maybe enchanted shield.
The other one on foot with something funky like terror helmet or enchanted shield and sword of might or striking.
To replace one of the wights with a wraith, I'd use the cursed book which adds a surprising amount of survivability to undead troops. With their low WS, most undead infantry are hits on 3s by just about everything other than goblins and slave rats. Being hit on fours gives you that much more lasting power.
Now that mounted characters can hide in units, I find myself using my mounted necro model a lot more. Heck, a 5+ armor save means something after all, and the horse adds another attack, too, an attack as good as a skeleton's for that matter.
When I try armies like you're proposing, I like the fluff of using lots of ethereal units, which makes a wraith, two banshees, and a spirit host really cool. Plus, that much ethereal stuff usually wigs out your opponents who expend a lot of magic trying to fry them.
And their efforts at stopping the ethereals can improve your magic phase. Roll two dice on a 3+ IoN to heal a single wound on a banshee or spirit host and watch your opponent drop two or three dispel dice in return, allowing to reserve dice for a much more need IoN for a new unit or to heal something else that you REALLY want to go off.