One thing that needs to be considered that has yet to be mentioned is the geographic location of the animal. This is a national website and the opinions are coming from all over the country.
IT IS MY OPINION that the deer from the southern regions of the country are more proned to react from noise by dropping their bodies in preparation for flight (jumping the string) than the deer from northern regions. I have no proof, but on most video's and tv shows I've watched- the deer doing any ducking are mostly from the south.
My thinking is body weight would have alot to do with agility.

MOST of the smaller/ wirier (110#=big) east Texas deer I've shot at have reacted to the shot. Some ducking the arrow some not.