Just look at their defense and goalie... nothing spectacular there, but Fergie still works his magic. Mancini would finish 5th with this team and so would most other managers.
You are giving him far too much credit when managers like Woy Hodgeson have managed to make teams with far less talented defenders defend much better. If anything, it shows a lack of tactical knowledge by SAF. He has a surplus of attacking talent that has bailed him out, and the Prem in general is weak right now. They wouldn't be in this position if Chesea and City weren't struggling.
Quit lying to yourself. Players like Young, Nani, Berbatov, and Bale dive almost every game. They are no different than Suarez. The Evra incident, which actually has nothing to do with diving, is what put Suarez under the microscope. The media painted him as enemy number one, and they just took diving as the next fault to him.