4 at the back would still mean Evans, Jones, or Blackett would have to start the attacks from the back and they're not entirely comfortable playing in that manner yet. Today wouldn't have been solved with a formation change. I think a 433 would be best in the long term, but that too will take some time to work as well as we want it too.
Even if it is true it isn't very accurate. In a back 5, with 2 central midfielders there are only 2 bodies in the central midfield, one less option than in a 4-3-3 where you have a third option. The importance of that third option is incredible as well, considering the amounts of triangles you can create, how close you are to make an offensive pass etc.
When Di Maria receives the ball as a left central midfielder with a winger placed further up, there is instantly a chance to either make a run behind the defense, move centrally to link-up or stay out wide.
Currently when our central midfielders receives the balls, the only simple passes are backwards or side ways out wide. In both cases it leads to absolutely no penetration even in the best of situations. If Valencia/Young beats his man, the opponent winger - it still means the opponents has their full-back ready to cover the damage.
How difficult is it for our opponents to defend when they know their two wingers can cover Valencia/Young all game with a rare few exceptions. Which means that if our opponents lets our back five roll the ball around, they have 8 men defending against our front 5. Those are some good odds for the opponents defense, considering in a basic counter-attack they are quite likely to attack 2 vs 3 which is a better situation than what we have.
When we are counter-attacking the odds looks brilliant for us, but LVG has realized quickly that we won't be able to counter-attack our way to the league title or top 4. Moyes realized that as well, the difference being that Moyes never had the experience to play in a dominating style - LVG does so he can adapt.
I know pre-season results mean nothing but the players looked like they knew the system, we were scoring plenty and creating a lot of chances as well as playing some really nice football at times. It's like last season is still haunting the players and there just like "holy shit we're back in the PL again" and the arses have dropped right out of them...bizarre, although injuries are playing a big part in this imo. 
