Canis said:
That's probably what I would do if I were a DM, but I'm not, so I'm interested in the opinions of others. I like the mechanics to reflect how things appear to be operating in the real world as much as possible, but I concede that my limited experience with the mechanics makes my judgement suspect. So... I continue to wonder whether people with experience with the mechanics think this is a good idea or not.
You are thinking too hard about the game. Stop thinking.

D&D reflects reality fairly adequately as long as people are around 1st-3rd level. For someone like that, a hit from an arcane archer for around 10-20 points of damage (d8 + bow enhancement bonus + arrow enhancement bonus + feats and other enchantments) will often be fatal. Problem solved.