I think there's a lot more that could be tested that what current implementation-centric interviews measure. At my company for example, I feel like we've gotten a lot of use out of our debugging interviews.
> What's even more rare is a UX designer that also thinks about these things, who are worth a million bucks.
Tell me about it. I've been struggling for years to get our designers to think of their designs as more than pixels on a screen. I'm really tired of having to be the accessibility police, or explain that small viewports and mobile devices aren't synonymous for the nth time.