Not sure if Patches are getting tested at all. New content most likely is. I meanto remember some people discussing that they have been testers for Grail Knight. We also know that WoM had an internal Beta / testing round. So I would assume that all major content updates are tested, maybe even by several independent groups.
However, there is the chance that testers have a NDA and aren’t allowed to discuss this. I fear FS are the only ones who can give you a conclusive answer if (and what) testing has occured since then with the help of people who signed up.