I am using Cross fire here with no issues. Both cards run at full clock speed and I see full uttilization on both GPUs. I've checked with CCC, GPU-Z, and MSI Afterburner. All show both GPUs being used. In a test I just ran in Lavender Beds with Full Screen mode and both GPUs I was 163 FPS, switching to border-less windows which disables crossfire it dropped to 87. This was with the game set to Maximum and at 1920x1080 on my main display (I also run in Eyfinity sometimes but find it distracting in this game).

I am using :
Driver Packaging Version: 14.20-140522a-172180E
Catalyst Version: 14.6
2D Driver Version: 8.01.01.1407
Direct3D Version: 9.14.10.01044
OpenGL Version: 6.14.10.12967
Mantle Version: 9.1.10.0020
AMD Catalyst Control Center Version: 2014.0522.2157.37579