Good points, but I still think you'll see them have a true mopper-upper in the back end, whether it's Woodford, McGee, Rodriguez, whoever. When you get a game like Saturday or the middle game vs LA, I think they'd rather use one arm for 3-4 innings whenever possible.
Just going by what they've seemed to prefer. Filling the pen with people who are a little more proven but who you don't want to use for more than 7-8 hitters could also work.