Vampires. Discussion.

Vampires in Heroes of Might and Magic V definitely became weaker. It’s hard to call them “higher beings” (as Lukyanenko would). Although in Heroes of Might and Magic IV, they were incredibly powerful. With 20 of them, you felt like a god, dominating the battlefield. Now, you need to gather at least 80-90 of them before you can deploy them without much fear...
It’s a pity that they were weakened so much. If they were worried about balancing the battles, they could have made them a 6th-tier unit instead of the Dungeon faction.