The Bobcats were one of the worst offenses in the league last season. Once you account for differences in minutes and pace, Diaw's stats were significantly worse last season than they were in 2005-2006.
05-06: 15.0 p/40, 7.8 r/40, 7.0 a/40, 52.6% FG, 30.5 assist rate, 11.5 TO rate, 10.8 rebound rate
09-10: 12.7 p/40, 5.8 r/40, 4.5 a/40, 48.3% FG, 24.2 assist rate, 13.3 TO rate, 8.8 rebound rate
So yes, I looked up his stats and your conclusion is wrong.
FWIW, AK outperformed Diaw in every one of thsoe metrics except for a/40 and assist rate.
This is why AK had a PER of 18.25 and Diaw had one of 12.8. That delta of 5.4 is massive. It's the difference between Deron Williams and Raymond Felton or between Carlos Boozer and Charlie Villanueva.