This happened to me last we. I tried everything that you have so far. Finally I did everything 1 last time & it worked.
Deleted HB folder
Uninstalled Microsoft Visual cc++ (all of them)
Uninstalled .net framework (all of them)
Uninstalled ALL other MS programs (except office & silverlight)
Rebooted
Run CCleaner
Reboot computer
Let Windows Updated re-install the MS program (had to check for updates manually several times till everything was installed) - confirm youhave the necesarry .net framework & stuff
Reboot computer
Re-install release version of HB
Run WoW in dx9
Problem solved.
As stated, I had already done this stuff, just not all at once. I did it 1 last time this way for shits & giggles - and it worked.