This has long since been addressed with a simple firmware update.http://www.appletell.com/apple/comme...ating-problem/
And what I have heard of overheating since then has nothing to do with the design of the cooling solutions, and more to do with misapplied thermal grease, which while certainly a problem, is easily rectifiable. I do wish Apple had learned their lesson from the 1G of MBPs though.
In as far as heatsink and thermal design, please feel free to suggest improvements, but having taken apart a few of them myself they do their job pretty well, and I have not had a problem with overheating in developing for 3D games on it(And I am not the only one doing similar work). So I would say that while there may certainly be room for improvement,your claim is fairly baseless.
As a side note, a quick(Key word) google search does not turn up any discussion on the overheating of MBA in about the past 5-6 months. That by itself would suggest that the problems have not been an issue in several months at least.