I like the way Vampirism works presently. I feel it's mechanical value would be negated by limiting the dice pools for thematic reasons. If it helps you try thinking of the vampiric mage as licking the blood up that is splattered on his weapon or clothes. When you wound someone with a melee weapon there is rarely a shortage of splatter.

As to the heal effects effecting demons and undead I feel that would be a poor design decision. It would make dark mages have a severe handicap with their minions. Think about the dice pool totals available on the heal spells compared to much more expensive combat spells. The value of mana per die of damage would be insane. Look into other heal effects such as renewing rain or group heal and it gets even worse. For gameplay stability they would have to re-work and nerf all heal spells and effects in order to make dark mages playable. I like this mechanic in Final Fantasy games but I prefer the current mechanic in mage wars for the above reasons.