Tactics against Necromancers.

However, you also need to consider the Necromancer's vampires. While you're busy fighting the skeletons, the vampires will devour everyone. Plus, there are dragons and death knights. The main thing when playing against a Necromancer is not to focus all your attention on the skeletons, so that the others don't go unnoticed. Therefore, it's better to use mass magic – slowing, prayer.