When using the newer drivers, have you already tried setting the power limit in wattman (slider below fan setting, slide all the way to right) to the maximum for your card? Either +20 or +50 for RX 480 I believe. I know that doing this adds much needed stability for RX 480 and RX 580. Don't know for sure that this fix will help but it does help many. However both of those games you list are have know issues with the games themselves with AMD and nvidia. Worth a shot though and easy to try, if you already have not done this.