LBE – minimal balance changes for Heroes V 3.1.

How many Vampires without Battle Damage Prevention (BDP) can take down an average Utopia?

You should know better, as you're planning to cut Vampires based on something. I haven't played the original in a long time.
Attach a specific replay showing specific timings where, in your opinion, solo Vampires are overpowered, and then we can work with that.
Are we talking about the grade? Alt was definitely overpowered; it just wasn't being fixed.