Necromancer tactics against Conflux.

Well, to quickly find an opponent on the map, there's a good spell – Air View.
-I only play 1-on-1, without any AI, so there's no need to get distracted by minor details. You go and eliminate the opponent as quickly as possible. I understand that we're discussing the Necromancer's tactics against a combined army, and if that's the case, you can't afford to be slow.
-The maximum number of Griffons is 5 stacks of 40 each; they're very easy to defeat. You just need to corner them. Then, the Vampire only defends against two Griffons, while the rest graze nearby.

I still don't understand how you plan to defeat two hundred Griffons with 12 Vampires.
1) Notice that all corners are occupied by Griffons from the very beginning.
2) You can't delay your turn because even a single regular Griffon will reach you. What if there are 40 Royal Griffons?
3) The Vampire himself has rather poor attack and damage stats, so 12 Vampires will probably eliminate 5-6 Griffons, while those, in turn, will kill a Vampire with 4 or 5 bites.
4) You probably need a hero with at least level 10 and decent magic (including Raise Dead) and maybe a couple of good artifacts – then it might be possible. But it's not a given that you'll have all of that by the second week.