I understand. This nerf is to hamper synergy of Vampires with other hero abilities or spells (Retaliation Strike and Celestial Shield) both in end battle and PvE. In the previous state Vampires are very high-gain-low-risk creature. This was unexpectedly raised by various members of the community.
We are open to any suggestions on how to adjust that strength into more controllable boundaries. So far we have not found any other.