https://bugs.winehq.org/show_bug.cgi?id=37189
--- Comment #9 from Yclept Nemo orbisvicis@gmail.com --- Using the updated client (second link few posts back) - the Gehn shard - resolves the sound issues. This most likely means the SoundDecompressor tool provided at http://forum.guildofwriters.org/viewtopic.php?f=86&t=4203 should also work, if you wish to run (nearly-vanilla) MOULa.
The Gehn client requires only an override for openal32 and not and msvc libraries. Since winecfg disallows overriding applications with the same name and the Gehn executable shares the name UruExplorer with MOULa, only a singe shard can work at a time.
Regarding performance, from limited testing I too find the game acceptable. Perhaps try running the game in a separate X server - outside of gnome3 I usually gain +20 fps.