There's always that rare possibility that the Thunder realize that they have plenty of offense on that team and doesn't want to be like those Suns team that score like there's no tomorrow and then fall short in the playoffs when the other teams ratchet up the defense. Those numbers don't really refute anyone's argument because nobody's arguing that he's playing great offense for the Thunder. Unfortunately, they don't refute the argument that he's important to their defense.
Yeah, that's cool. We can also ignore the poor rebounding and shot blocking.
Oh, by the way, you reference "those Suns teams that sore like there's no tomorrow and then fall short in the playoffs when the other teams ratchet up the offense."
In 2006-2007, the Suns won 61 games and lost in 6 games to the Spurs in the 2nd round. Their defense was 16th. This year's Thunder team? 15th. In 2007-2008, when the Suns lost in the 1st found and won 55 games, the defensive was 17th.
The point being - the Thunder, even with Perkins as the "defensive anchor" isn't actually a very good defensive team and on the same level of those Suns teams. Yes, Perkins helps when he's on the court for his 25 or so minutes. But the fact is - he's just too deficient in too many areas of the game to stay on the court for more than 25 minutes and therefore, isn't really all that helpful to the Thunder team.
And also, he got a giant extension that is already not worth it.