How to defeat Death and its vampires?

Yes, the best solution is to install Equilibris 3.51. The balance is quite good there, better than in Armageddon's Blade.
On large maps, Necromancy will certainly be useful, but firstly, it will require some skill, and secondly, the number of summoned creatures will still be smaller.

As for Armageddon's Blade, there are few chances against Death, but something can be done.
First of all, you should create several mage heroes who will use hit-and-run tactics to thin out the ranks of the fanged creatures. Secondly, you should actively use the town portal; it can also be used for effective hit-and-run attacks, as you can teleport directly from the battle.
Thirdly, you should properly develop your tactician, and during the battle, use teleport to pull the enemy closer and quickly defeat him. After his death, the vampires will be significantly weakened.
Also, don't forget that after being destroyed (disintegrated), vampires cannot regenerate.