In reply to DaveSpectre122:
Making it manual then. I did try to use the set property before, probably got nothing from the variables to subtract, maybe making if then cases that identify the unit type and make integers for the amount to subtract. Sounds solid enough.
In reply to DrSuperEvil:
I'll do another search for that.
Small update from my side, and for those who are interested. Yesterday late I used the deal damage action with the triggering units damage effect setting. While is wasn't the values I wanted. It did work in that each unit killed subtracted life from the target.
I'll update when I have new insights.