The only buffet I can think of that Universal Orlando has ever had was the "Studio Stars Commissary," in what is now the Monsters Cafe. It had pastas, meat carving station, salad and desserts. It was okay, and a good value given how much my family would eat, but it didn't last very long. I probably have some photos somewhere in old photo albums from the early nineties. I liked the autographed celebrity photos in the walls.
Disney does buffets well. Not sure Universal would to be honest.
I guess Trattoria del Porto at Portofino has a breakfast buffet, but not much too it.
Oh, doesn't the Royal Pacific have a Luau? That's a buffet isn't it? Is that good? Only select days though?