Why are you so fixated on the Necropolis? The Warlock will arrive at the end of the first month and deal 4000+ damage with an explosion – there won’t be enough Vlad to handle that. As for transforming creatures, I’ll build my second Castle, especially if I capture it early, to generate 1000+ income and have a market – goodbye. You’ll have to invest resources and money into it, which will negatively impact your own Castle. After all, transferring troops is effective for 4-7 levels because there will be many skeletons and native units, but zombies and ghosts aren’t that decisive unless the map is small. But on small maps, you don’t really think about a second Castle; the game lasts for weeks there.
But a couple of hundred Obsidian Gargoyles under Heavenly Shield are something else entirely. I spent half an hour with my entire Necropolis army, under Armageddon, killing 700 Gargoyles with a shield and evasion.
Oh yes, against those skeleton archers, I cast Mass Evasion once, and half the problem was solved. And against the entire army, Mass Slow, and all problems disappeared. If you can’t cast Mass Slow, cast Single Slow on the skeletons individually; they’ll move twice as slowly, and Necromancers rarely have Dispel or Haste.