Even in the Pre Crimson drivers including 15.7.1 the core clocks fluctuate and drop down to as low as 300 MHz in games when crossfire is disabled. Causing low fps
I always install my drivers properly using amd uninstaller and ddu in safemode.
Since windows 10 all of the available amd drivers for my r9 295x2 have caused issues with clocks dropping and not being stable at full.
The only stay at full when you have crossfire as default.