I assume you already disabled shadows? And did "winetricks vcrun6"? ( http://appdb.winehq.org/objectManager.php?sClass=version&iId=19045&iTestingId=48557 ) http://wiki.winehq.org/Performance may have a few tips, e.g. try disabling glsl. If the problem persists please file a bug at http://bugs.winehq.org with recipe to reproduce problem using the freely downloadable demo.
