LBE – minimal balance changes for Heroes V 3.1.

Try reducing the percentage of necromancy; then it will be more difficult to gather only vampires from it, resulting in fewer vampires in your army (but more of other units).
Currently, as far as I remember, you can deplete the dark energy reserve for the entire week in just one battle; under such conditions, it is easy to assemble any overpowered army, not only with vampires but also with archers.