I agree with whoever it was mentioned the Sheaim.
Get the AC high enough and you can be getting 4 units a turn, easily enough to take on one unit every 4 turns even if it does have 200 xp.
And it shouldn't be too hard to get a summoner in every city you own summoning nightmares that last 3 turns with fear. The vamps would have a hard time just attacking you, not even mentioning all the summons you can swarm on him once he comes at you. But thats a defensive strategy, and you will want to go on the offensive. Just remember- stacks of summoners with nightmares (wraiths when you get eaters of dreams). And just keep working on raising the AC to get more out of your portals. you are going to have so many units you will want to kill them off so the maintenance doesn't kill you.