It actually all boils down to mathematics. The maximum product of range times arrow speed at the end of the flight path results when you fire at exactly 45° relative to horizontal, as well as greatest total range. At lower trajectories, range goes down while arrow speed goes up; at higher trajectories, vice versa. So in order to accurately render archers' range, the animations should have them fire at 45° at first. This would be shots at extremely long distances, with a lot of power, but greatly inaccurate. As the enemy closes, the archers' trajectory should become flatter, resulting in even more power, but shields and body armor might be a lot more effective. Archers should never fire at more than 45° relative to horizontal: Not only would these shots become highly inaccurate, they also wouldn't pack much of a punch.