Ladies and gentlemen, I have the most amazing news. Pretty much the best news I can think of.
I have finally received word back from the Mali Developers. They revisited the issue and found that the fault was indeed in the Mali drivers.
"Following previous emails, the Nexus 10 issue that you have been mentioning has been fixed in the latest versions of the Mali driver."
It is, unfortunately, Google's responsibility to release this new driver version with the next Nexus 10 factory image. We can only hope that the fact that I/O has come and gone and the recent release of the Google Edition S4 and One on 4.2.2 does not mean that JB 4.3 or KLP are a long ways out.