I was there, too (tenth row) and Patti's diction seemed fine to me, even in Not Getting Married. However she did do it quite slowly, so that may be the reason. Also, I knew the lyrics to nearly every song they did, so it may be that I heard everything clearly because I knew what they were singing.
One other thing I noticed, Patti came to the edge of the stage several times and seemed to be pointedly scanning the audience. I don't know if that was part of the choreography or not, but it seemed rather pointed to me.
Sarcasm is an allergic reaction to stupid people.