Flockhart comes off as too vulnerable to play Phyllis, IMO. I love her work in ALLY MCBEAL, BROTHERS & SISTERS, and THE BIRDCAGE, and in all of those she always has a vulnerable edge to her that I think would be too much for Phyllis.
Griffiths is one of my favorite actresses ever, but I see her more as Sally than as Phyllis. She sang karaoke in BROTHERS & SISTERS a few weeks ago, so who knows? Maybe she can sing? :)
I suggested Mary-Louise Parker as Phyllis in another thread, I think she would be marvelous in the role. I'll pass on Bening and Catherine Zeta Jones though.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"