https://bugs.winehq.org/show_bug.cgi?id=46068
--- Comment #2 from Zebediah Figura z.figura12@gmail.com --- Well, this is not necessarily going to be easy to track down.
As I recall, SW:TOR needs the Staging patches associated with bug 29168 to work. As far as I'm aware, this is all that's necessary, but I could be missing something. It would help if you could test whether upstream Wine 3.17 and 3.18 show the same performance degradation, by applying just those patches to an upstream Wine tree.
If so, the next step would be to do a regression test from 3.17 to 3.18, unless someone has an intuition of what might have changed.
If upstream Wine shows no performance degradation, then something must have gone wrong with Staging, and the most helpful thing to do would be to perform a regression test between Staging and Wine to find what the problematic patch set is.