Not quite 4k but I have everything on max on 3440x1440 and I have no issues whatsoever. It actually looks better than I was expecting tbh.
I've got a real weird issue, the game's so vibrant it actually gives me a headache, my monitor is perfectly calibrated, so it's weird!
Last night, it was unbearable trying to find mobs. So again, won't be playing for a few weeks.