You could use the modifier regen to heal overtime, as a passive skill for a custom class for example. Or the modifier could be an item giving the regen modifier again. Modifiers list can be found on the wiki here: http://wiki.heroesofhammerwatch.com/List_of_modifiers
and you can modify it further with scaling based on other stats that are applied to the player like the chapel's lifeleech path.

I was also thinking about something like duke signet ring area of heal but instead of healing base on max hp make it heal base on current vampirism

If that make any sense