Apologies if you've already tried this - have you run the AMD driver removal tool before installing the latest driver version? I had similar issues with my AMD Graphics card on a couple of MMO's (especially in areas where there was a lot of re-drawing going on) which seemed to be resolved doing this (well, until the card itself developed a fault and I swapped it for a Nvidia). Informed that sometimes some files are not properly updated which can cause problems.

I'd also recommend disabling Freesync if using that.