I've had a few oddities when using Hunker skill. 

He either shoots in a different direction than where I'm aiming or doesn't seem to shoot at all. It doesn't seem to be tied to a specific weapon. It does seem to happen when there is a lot happening on screen. If I action the skill and then switch characters it appears to work fine, in that the AI seems to be shooting critters as intended. 

I've tried recreating but couldn't find a common thread. I'll continue testing and try to get a good clip of it.