In my experience with Dreamgirls, Effies have just as checkered a history as Momma Roses. Effies generally don't get through eight performances a week, and many do lose their voice or sound hoarse. Lorell has the one killer number, but it's a lot less demanding than Effie's role.
But consider this... Effie has a tough first act, and then disappears for long stretches of Act Two.
In a show with about two and a half hours of material, Rose is offstage for maybe 20 minutes total (around 2 minutes for "Little Lamb," five minutes for "If Momma Was Married," five-six minutes for "All I Need Is The Girl," and then in Act Two, about five minutes for "You Gotta Get a Gimmick," and then the sections of the Gypsy strip that don't involve Rose in the wings. When Rose is not singing, invariably, she's screaming at someone. Now that's a workout.
"Gif me the cobra jool!"