I like this adaption of the Lean Startup ideas for UX design with the pivot that you should start the process with learning before building. It’s a very typical dev temptation to code first and ask questions later. A temptation worth resisting unless you like to throw away code.
I also agree that paired design can increase the quality of design–I’d say also that unless the two designers are identical clones, it will allow each to focus more on their individual strengths which is another reason the quality of output should go up.
http://www.cooper.com/journal/2011/03/more_better_faster_ux_design.html