I loved Patina in this show (and really enjoyed the show in general the times I've seen it) but I don't think the acting performance Patina has been giving in the show is really that far off what Raven does already. I'm with somethingwicked here. In fact, I think Patina is closer to the Raven mold than she ever was to the Whoopi-in-the-movie mold. And it seems Raven is trying to break out of the Disney sitcom star mold. The role requires a tremendous amount of presence and sass, and I think even her body of work in the past, limited though it may be, shows that she's exuded that her whole life, since her days on The Cosby Show.
And, further, I respect the producers for pursuing this kind of star casting over Whoopi as Mother Superior. As has been wisely pointed out on this board, the role on Broadway is much more vocally difficult than it was when Whoopi played it in London.
PS, in looking for clips of her singing on Youtube, I found this interview/performance on a talk show when she was very young. Am I the only one who thinks she seems exactly like a Young Deloris would be in real life/the way she was played in the brief bit at the beginning of the film?
http://www.youtube.com/watch?v=WhzNL9D7NL4
"Art, in itself, is an attempt to bring order out of chaos."-Stephen Sondheim