This role requires an actress that has extreme personality. She needs to be larger than life, and she needs to chew up and spit out every inch of scenery on that stage.
I saw Sara Ramirez several times in the role - and she was the show's saving grace for me. Absolutely brilliant. She's as irreplacable as Jan Maxwell was in CHITTY CHITTY BANG BANG, and as Beth Leavel is in THE DROWSY CHAPERONE.
Absences or not - she was absolutely marvelous in the role.
Upon seeing Lauren Kennedy, I was honestly embarrased for her. She tries too hard to be funny, and isn't funny for a split second. She has the comic timing of a peanut shell, and the vocal chops of Sherry Lewis. She has a gorgeous voice - but it's not write. It would be like Sarah Brightman playing Eva Peron. Not a chance.
Orfeh is the closest obvious choice I can think of - but whoever it is, needs to get in there fast. Kennedy is abominable.
"If you are going to do something, do it well. And leave something witchy."
-Charlie Manson