Mundus was nothing special, but it is not the worst. the worst is the Succubus, imho. Fightin in the TV and Bob also felt better to me. Mostly because of the Rez-vibe, and the great mechanics of avoiding his 3-4 attacks, based on seeing the color and the color only, at first.
Also, needless to say, Vergil was not designed for us. We know all of his attacks already without even seeing them first. I am looking forward to how he gets harder in new difficulties, cause the Vergil fight was still the most badass part of the game, imho. Another great fight was the Mundus Spawn. Am I missing one more somewhere? Oh, the first boss. Nothing special, but mechanically great, and has very few interruptions.