Examples of medieval-style archery
This archer here has studied medieval and ancient styles of archery, which include holding your payload in one of your hands (either the bow or draw hand), placing the arrow on the right side of the bow, rather than left, and it's success at firing rapid shots with fairly high accuracy.
This lends a LOT of credence to the idea of being able to fire 4+ arrows in 6 seconds (1 round) at level 20, since he's shown to fire 4 arrows in 4 seconds while moving.
There's already been at least 2 threads posting the same video, please double check before spamming the forums