Why win shares? Why not PER or advanced +/-, or simple ratings, or ORTG/DRTG differential or an aggregate of PER36 stats or whatever?
One stat I would like to see that might be as relevant as the one you chose is the sum of All-NBA teams, All-Defense team, All-Star teams and Finals appearances. Yes, being voted onto these teams and getting to the Finals is a bit subjective but I think the amount of times a position in the draft would appear in these stats makes the overall way of viewing the impact the position had relative to their teams extremely relevant.
I will say, TP for the excellent thought process and collection of stats. The win share data does confirm some things I thought, which was, picking first and third was awesome and that way too many teams reached at #2. Also, I felt there was a couple of positions in the teens that yielded top ten results which I interpret as, if you have good scouting, drafting at 13-17 is really not all that much different than drafting at 7-10. Of course the main caveat there is you have zero shot at turning a 13-17 position into a top 3 position prior to the draft whereas 7-10 does have a slight chance of upgrading to a top three position.