Experiencing performance problems RX480 8GB. This is a system built only 2 months ago so I don't suspect OS or other component issues. Playing a game such as Overwatch, performance starts out silky smooth at 60FPS. The longer I play, however, framerate starts to dip eventually into the high 40s. The worst offender is replays which can hitch down to 30FPS (this occurs pretty early in playing). That particular glitch is odd as the actual gameplay can be running at 60 FPS but the replay runs in the 30s and 40s. I have also experienced issues with FarCry 3 which consistently runs poorly (in the mid-40s, which I was able to obtain easily with my much older Radeon 7870 with the same settings). Drivers are up to date.
I would also note that heat is not an issue. There was an earlier driver that didn't seem to do fan control properly so it did throttle at that time, but haven't seen that since upgrading the driver (it keeps itself pretty consistently between 68 and 84).