@Aronida I may be wrong, but i think, if you are on the verge of ballista's effective range or farther, impact may be reduced.
@SingLove Yeah, that's probably what is happening, although i would image it is not that easy to dodge something that fast, even if you know the trajectory, i believe enemies wouldn't be so stupid as to fire at them when they have already retreated. So i guess, troops are just lingering at the periphery of effective range, not coming any closer, but still showing them chance to land a blow,