[Xietor]

One major flaw in the Ai is to life drain different targets, instead of focusing on one and killing it off. Be nice if this was fixed.

My guess is if you check the drain life was spread around, and did not hit the same target each time. If the unit is not lifeless or had luck, the target took drain life damage. It cannot be resisted.

Other exception, damage went to blood slaves. Or the unit was getting healed from some source. But drain life is not resistible.