I regularly play Necropolis in multiplayer – I win in 80% of cases. All your highly praised heroes won't help against Plague plus Unholy Word. Besides, there's a feature for Necropolis in artifacts – Sar-Iss's Robe and the Crown. After that, Liches cast Plague incredibly effectively. You can even just sit in defense – I've done that many times.
The supply wagon and ballista are taken down by skeletons (which, admittedly, aren't very effective in other situations). But I disagree with the statement that something was nerfed – on the contrary, they strengthened an already invincible faction.