One thing that made me think Sara Kaufmann is underestimating Ronda was her comment on the media call that,
"An armbar is only one technique, though of course Ronda has multiple ways to transition into it."
An armbar is not just one technique. There are several techniques that are a bent armbar, a straight arm bar. I'd question whether a straight armbar you do with your opponent on her back and one you do when the opponent is on all fours and you hook an arm and turn toward her hips are really the same technique, even though you end up with a straight arm.
For more detail and a little set theory, check out my blog post months ago on Why armbars are hard to avoid.
Really, to say, "She just does an arm bar" is like saying about a boxer "He just punches people," or about a judo player, "She just tries to throw people on their back"
Somehow, even though every boxer in the Olympics knew that his or her opponent "just punches people" every match I saw, both people got punched a bunch of times. Lots of judo matches, I saw people get thrown on to their backs, even though they knew the opponent was going to try to do that.
Funny how that works.