Oooh -- those are delightfully thought-provoking questions. I don't think I've ever been involved in an Agile process that included Doc in the core team, but now that you raise the point, that's clearly a process failure. (Indeed, I suspect that having Doc involved from early on would bring UX benefits.)

Of course, I've too-rarely worked anywhere that had genuine professionals doing the documentation to begin with, which says something in and of itself. Yet another reason why I desperately want to have enough money to staff Querki properly...