I worked with an excellent QA once, and that changed my perspective completely as a dev.

A great QA can understand the features of a product quickly, turn those concepts into some sort of grid or matrix in their mind, then pull a bunch of paths and scenarios with estimated priorities and probabilities at a fast and efficient pace, all with great coverage. They can also identify features contradicting each other more quickly than product people.

I think a good QA is capable of being a great vibe coder nowadays, too. If you can write great test suites (write names only), agents nowadays are able to turn those specs into decent codebases. Comparatively, I know a lot of decent dev having not very good taste in testing, who often write overlapping tests or missing important paths.