http://bugs.winehq.org/show_bug.cgi?id=36399
--- Comment #20 from wineuser sickam@mail.ru --- Disabling the ingame UI of TERA leads to a drastic FPS increase up to 400 %. In places where I get about 25-35 FPS with the UI, I get over 80 FPS with the UI disabled. Places I get lower FPS, about 20-25, i get about 60-70 FPS with the UI disabled. And places with even lower FPS (which includes cities, instances, crowded areas, ...) I still get around 30-50 FPS.
Too bad, that the game isn't playable without the UI.
This seems to be a common problem with the game. The UI was made with a software called Autodesk Scaleform (http://gameware.autodesk.com/scaleform).
However, i talked to people who told me that they tested the game on WINE and native Windows and compared the performance. They all agree that the game runs much better on Windows. In this case i don't consider this bug fixed yet.