I have used plenty of Vampire Spawn, but I dont want to metagame. You stated Digger knows that it cannot heal radiant. Does he also know that radiant stops it from regenerating ALL damage for the whole turn?
Yes, sorry if that wasn't quite clear. Digger knows if he takes any radiant damage he will not be able to heal from other wounds taken at about the same time, (i.e. in the same round).