I completely agree with you that technically the armorer is at fault traditionally in these types of situations and a jury may in fact find that to be true in the eyes of the law eventually, but I find it interesting that in this case the armorer was a younger attractive female on a rough n tumble set and I can only assume there was pressure on her from the other people there shooting if not Baldwin himself to go shooting. Hell she may not have even known the guns were used but that's not really an excuse.
What is a meditating factor is what Baldwin said, told her and ordered her to do. Remember he's her boss. I'm assuming there's evidence he told her to do blah. If so imo he deserves more than 20%.