No, but it certainly was a huge part. His defense was quite good, but all season long, he was known for getting thashed by any good big man, whether it was Dwight, Pau, Timmy, Randolph, or Bynum. But he was by no means a defensive equivalent. That would be selling Dirk's offense quite short.
No, Marion and Chandler were great defenders. Kidd had some good moments against Kobe and Durant, but frequently got his age exposed. Stevenson was decent, but not great by any means.
Were they hot? Or did they perhaps regain their early season chemistry? Don't forget that they played at an extremely high level for the first half of the season, until all the injuries hit. They were on pace I believe to win around 65 games until the injuries killed everything.
I agree he was.
What is wrong is to only mentioned the good things the supporting cast did, and absolutely none of their shortcomings, with the sole purpose of dismissing Dirk's run. You can't even begin to claim that you have an objective view of this matter without looking like the got you are.