The resolution of TVs and monitors marches ever upwards, and this game only has few limited options for UI scaling. Many games have either a single UI size that is maintained across all resolutions, or let you scale the UI size freely with almost no limits.
Unfortunately this game only lets you scale the UI to a maximum of 140%, which is not adequate for players on 4K (3840x2160) displays. This is how the UI looks on a 4K display at the maximum available scaling.
That's the largest that text in chat log can get too. The nameplates above players' heads ignore all scaling options and get tinier and tinier the higher the resolution gets with no way to increase the size. The rest of the UI you can see, including the microscopically small buffs bar. The boss HP bar and boss buffs/debuffs are equally tiny.
It would be really nice if the devs gave us free scaling of the UI, but at least add 200%, 240%, 280%, 300% UI scaling options if this is too hard. Add more size options for text in chat log too. And also fix the nameplates above players' heads not scaling at all!
NOTE: If you aren't running a 4K+ display, simply display that image in full screen in your browser to see how the big the UI actually would be on your display.