As a matter of fact, I work as a software engineer in QA. But like you say, it's not technical issues that become worse in patches. It's design issues. No amount of technical QA can do anything about that if the designer doesn't listen. It certainly won't turn any lights red in a continuous integration system or anything of the sort.
The technical issues were merely not fixed when the patch notes said they were. I still sometimes can't get into /ops chat in warzones, I still sometimes get randomly booted back to character selection, warzone wins still don't count for the quest, ability delay is still there, and so on.