I have been working with the Battle.net tech support on this issue. They want to bounce this ball into your court now. The problem is the game is running in slow motion when trying to play Diablo 3: Reaper of Souls. Here is what the tech support person told me to tell you:
"Getting the catalyst up to date and for assistance configuring Crossfire or the APU to work with Diablo 3. I believe it is defaulting to the slower card and its causing massive slow down within the game."
I am running Windows 7 Home Premium.
Model: HP Pavilion dv6 Notebook PC
Processor: AMD A8-3500 APU with Radeon(tm) HD Graphics 1.50 GHz
Installed memory (RAM): 6.00 GB (5.48 GB useable)
System type: 64-bit Operating System