I agree with you on Rio and Vidic though, top quality defenders (which neither have been for some time) were needed at least a year ago and Moyes not doing anything about it was one of many things that cost him his job. I'm quite surprised van Gaal hasn't done much about it either.
But yeah a diamond formation would make sense, at the risk of sounding like a manager because I've put too many hours into FM myself someone in both the holding role and attacking midfield would benefit the defence rather than having one player trying the box-to-box idea - as we've established you don't have anyone capable of that currently in the team.