I must admit that I was hugely surprised as I saw this video.
That's not at all how I play an archer there !
And even worse : It's imho much more difficult than it looks like there ! At least at the beginning.
In my opinion, the video was done by an absolute professional, someone who plays the game for many months now.
This archer acts far too agile for my taste, and far too much than I would be able to play him.
This "jumping back", by the way, is just kind of a work-around around the fact that you can't step back fast enough from enemies (at least in the beginning of the game). This is necessary, because so far running backwards away isn't properly implemented - at least for my taste.