Maybe sort it by round, or by replacing your Rk with an Offense/Defense designation.
2011 was skewed to Offense, 2012 to Defense overall. Eyeballing the data it looks pretty even, especially over the last 3 years.
There have been a lot of R1 picks on Defense (Randall, HaHa, Datone, Perry), with Bulaga and Sherrod between the Raji/Clay picks of 2009. I have no problem with the R1 picks being more defense -- it seemed like that side of the ball needed a lot of talent.