The stoppage was early and here's why:
YES, McMann was dropped and wasn't intelligently defending herself in the 2-3 seconds that she was recovering from the shot, BUT 1) She was already starting to get up when Herb Dean actually stepped in to separate the two.
2) She's an olympic silver medalist wrestler and Herb Dean needs to take that level of toughness, fitness, and cardio into account there, liver shot or no liver shot. Some people can recover quicker than others from those and I believe McMann should've been given that opportunity.
3) IT WAS A TITLE FIGHT. Both fighters need to be given the benefit of the doubt because the stakes are so much higher. Whether thats technically the right thing rulebook-wise, or completely politically correct, is irrelevant because it's the truth. Stoppages need to be definitive, as in no doubt about it to any viewer, if for no other reason than because it's the last impression left in the mind of the viewer. For that very reason, a questionable stoppage in the main event has the ability to taint the entire card in the viewers mind, and hurts the UFC as a result.
Truth be told, I think Herb knew he screwed up in the Waldburger fight, and wasn't about to make the same mistake twice in one night. Herb Dean's reputation as the best ref in MMA only continues to exist based on past performance and because Dana White perpetuates the claim. I, for one, have never bought into that claim, and his recent performances only prove that point. He's one of the best, no doubt, but he's no Big John. I'm sure that had Big John been reffing those fights, we wouldn't be talking about late/early stoppages.