I currently have 2 * RX 480s I have been having this issue on the previous driver and currently driver version 19.6.1
Basically when playing World of warcraft, fully up to date btw, when I have it set to DX 12 the game crashes. When it is set to DX 11 it does not crash at all. I have reported this as an issue over a month ago to AMD and thought it would have been fixed in the most recent driver update. I have tried clean installing the graphics drivers and all sorts and nothing seems to fix it. I even read on another post someone reseated the cards and dusted the inside of the PC I also tried this and it did not fix it. I mean the game runs fine on DX 11 anyway so it's not a major issue, but I like the look of DX 12 better. Hopefully this can be fixed? Also please post if your having similar issues.