http://bugs.winehq.org/show_bug.cgi?id=11674
--- Comment #11 from Anders Aagaard aagaande@gmail.com 2009-01-06 08:10:11 --- When windows juggles threads I believe task manager shows each cpu at 50%, with a total of 100% cpu usage.
Now you'll never see 100% utilization of all cores in world of warcraft, it's a game, so a lot of things rely on eachother, so multithreading it efficiently is hard.
Now looking at the original bug report "only one CPU is given significant tasks", I wouldn't consider this a bug unless it's different on windows. I'd assume it uses one cpu for most tasks, and multithreading for extra things (loading seems to be one thing where they fork work into multiple threads).