I recently gave Diablo 3 a spin since last driver update, and had to see that there is roughly a 66% drop in frame rate.
I am using a Lenovo Z50-75 notebook, AMD FX7500 + AMD R7 255M + 8 GB DDR3 RAM. The issue holds for both single dGPU render, and Hybrid CrossFire enabled. (It would be nice to now if the latter is supported by the driver or not. I generally tend to enable CF for all games from CCC, and in Diablo it did seem to increase performance signifacntly.) Before, with CF enabled the game was playable in native fullHD resolution on lowest settings, now it chokes on 1280*720 too.