I don't think I have missed the Crocs in the City quest perhaps more than once or twice since it was added to the game, but I am having rotten luck getting all 4 beasties. I've had Toothy twice and Muckbreath once on my main, and Muckbreath again on an alt.
Has anyone managed to get all four? Do you get many duplicates? (Deleting that second Toothy felt so awful ...)