As good as it gets? For him, you're probably right, though he has added a little polish to the current character, e.g. the shoulder roll to prompt the "Feed me more" chant. Nonetheless, with that many years in at the major league level and his "skill" level being where it is--rather than, say, working to improve his techniques and improve where he's weakest, all the time he was characters before Ryback was created--it suggests this is about all you're going to get out of the man.
Should also note that in some cases--predominantly in the WWF/E--powerhouses are booked to only have so many moves in their repertoire, which I suppose the Cena-haters probably don't want to hear despite it being the truth. Am not saying that's the case with Ryback, just talking generalities in the company history.