We just got off the Trans-Atlantic Celebration Cruise and we were also on the Mardi Gras last year for its 5th outing.
I can confirm that there were 2 comedians most nights in Punchliner and Limelight with overlapping showtimes. Overall, I think we had 6 different comedians over the 14 day itinerary, with the comedians "swapping out" on day 7.
In addition, they also had a couple special comedy shows with the comedy headliner in the Grand Spectrum theater. We saw Happy Cole in that Spectrum Theater and he was hilarious.
If Celebration follows the same pattern as Mardi Gras, you'll likely have 3-4 different comedians rotating through the venues on a 7 day cruise.