I find it quite useful. I mean, you have a thrall, 1-2 wounds left. Charge, attack, attack, demise, and taking out markers? I don't think it's expensive at all. In fact, I see it as a good mechanic for the keyword witchling. I think the sanctioned spellcasters used to have something similar in M2E (I don't remember exactly bc I didn't use them too much). But I might be mistaken