I really don't like to shoot them while walking either but after a few kills I realized it's not that big a deal. My aiming point (depending on distance or speed of the deer) will only vary a couple of inches.

I think even a marginal shot will have better results if the deer wasn't on alert before the shot. They just don't feel the need to continue running.

You have to understand how they think. and the manner of which they compute things. If not on alert and presented with a sharp pain, it seems like they equate that with the immediate area they are in. They all seem to "get out" of that immediate spot very quickly (10-30yds) but then once cleared, they will stop and some even have looked back with curiosity before becoming weak and fall over.