Vampires in the 5th installment definitely became weaker. It's hard to call them "higher beings" (as described by Lukyanenko). Although in the 4th game, they were incredibly powerful. With 20 of them, you felt like a god, walking around and dealing damage. Here, 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!