Thanks for reporting this issue! The fix I was going to suggest involved copying a dummy .exe file to 'C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE\devenv.exe', then setting up a registry entry to convince the MSI that Visual Studio is installed, when actually it isn't. Reinstalling Visual Studio is another more time consuming way to solve the issue.
The problem is that the MSI is not differentiating between install/uninstall actions when evaluating its preconditions. I'll note this down for a fix in a future release. Sorry for the trouble.