I play in 2160p on a 4K TV and in general the scaling is very good now. In the previous expac, the game was straight up unplayable above 1080p so what we have now is a significant improvement from before. There are a few things which are still small, the NPC text bubbles above their heads is a good example of this, but in general the UI is completely usable in 4K now which makes me happy.