Thank you for bring this to our attention. We've been using your testcase at http://bagnell.github.io/cesium/Apps/Sandcastle/gallery/OIT.html to try and replicate this on Windows hardware. Thus far we haven't been able to replicate it on Windows, which is the only GL driver that Intel creates. If the error cases are showing up in OS X, then you'll need to raise the issue with Apple, because they create the driver for OS X. We don't have the insight to know the code paths taken by that driver.
I'm sorry we can't be of more help. Good luck.