SC2 and Diablo will run the computer REALLY hot, and those 11 inchers are made more for writing and doing some basic design work. As you would guess, any computer with integrated graphics will cause some issues with the MBAs. I will say that the games will run and for the most part be decent, just not totally awesome when playing the game.
To be more specific, I think SC2 runs at around 30-40fps. I play GTA:VC on my computer and it runs well too, but those are PS2 graphics ported to a computer. Diablo 3 is probably really intense and would need to be run at lower settings.