I definitely agree that MC does need new bosses. Maybe a slightly wider array of midgame stuff? Because you've got your basic mobs (zombies, skellies, creepers), but no real boss for Overworld. Then you've got Wither for Nether, and Edna for the End. I mean, I guess you can consider Endermen psuedo bosses for the Overworld? But... a good enchant on a diamond sword, and dead Enderbutt.