[Gethe]

This issue is, as it's core, an artifact of how the UI is rendered in WoW. Everything is in static pixels, and when you scale it up or down things get distorted. With the default UI it's not a big deal because all the textures have a fairly rough grainy look to them anyway, so it's not really noticeable.

In RealUI though, pixels matter, so using scale isn't really a good solution. The only real way to accommodate 4K, or really anything higher than 1200, is to make an element's static size bigger/smaller based on the screen size. I've done this to an extent with the HUD config bar, but extending it to the entire UI, including Blizzard stuff, is no small task.