I have only seen Carol Channing on stage once with Mary Martin in "Legends." I agree Carol Channing was holding the play together, to the extent it was possible. The best moment was Mary Martin not being about to stop laughing when the male stripper said something to her.
I saw "Legends!" on a Saturday afternoon in Boston, by then Mary knew all her lines. Even years before "Legend!" Mary took longer that most people to leaning the lines, as far back as "South Pacific" and the revival of "The Skin of Our Teeth."
source: the recent Mary Martin bio. by David Kaufman