Weird, I don't know what's happening then. I've been hitting them with all the quickhack DoTs and laying into them with a monowhip, and then just back off when they're down to a few percent at which point the bleed, burn, or poison incaps them. If you're using a blunt weapon be careful you're not hitting them after their health hits 0, because at that point any further damage will kill them, even nonlethal.