ATI Crossfire dont work for me with crimson 16.8.2. on F1 2016 only one GPU goes on 100%. The Frames max at 32 on
3840x2160 with high Settings. Disabling Crossfire on Controlpanel gives me 40 - 50 FPS in the Game and works better.
Asus Rampage 5 Extreme
i7 3930k 4,5 Ghz
32 Gb DDR 3
2x Ati 295x
Crossfire isn't a guarantee for every game out there. Some games have negative scaling and will perform worse with Crossfire turned on. Thats on the developers shoulders, not AMD's.
Check under the tab for your game in Wattman and see if there is a crossfire profile for the game. Sometimes that will help. If not, then you're going to have to disable the 2nd card via wattman each time to play until it gets patched to support it better.