Danny appears to be right; when Leon left after the '09 season, our rebounding took a pretty substantial hit. I don't know if that's due to a change in philosophy, or if it's solely personnel related (replacing Powe with a perimeter player like Rasheed didn't help a lot.)
Those stats also support why Perkins was expendable and traded - you don't pay some one $10 mil for defense alone.
I don't think you can attribute team statistics to Perk. For instance, in 2010 Perk was first on the team in total rebounding percentage, and third in offensive rebounding percentage. Last year, in limited minutes, he was 1st in TRB% and second in ORB%.
Perk was this team's best rebounder. It's hard to fault him for whatever deficiencies we had in that regard. Sure, he could have been better, but so could have everybody else.