[phamilton]

UX is about empathy. Understanding how other people think and the emotions they feel. All those tools you mention are metrics to keep score, but without an understanding of how your users think you are playing a fun game of guess and check. Sure with enough iterations and metrics you can figure out anything, but your users won't give you that many chances. Someone who can get the initial design in the right ballpark and use metrics to fine tune it is your UX guy. As I programmer I really struggle putting together a viable initial UX, and I don't think I'm unique in that struggle.

Quite frankly, it's because I think very differently from most people and have trouble understanding their thought process. I'm not introverted or especially socially awkward or any of those engineering stereotypes. Everything from my ability to creatively approach problem solving to my subtle dry sense of humor is because of my different way to think about things. But when I need to think like everybody else, I just can't do it. That's why I need a UX guy.