One could make the argument we don't have the players for any formation, then. We don't have top wingers for the straight 4-4-2, we can't use the 4-2-3-1 with Seba and Camo because that would bench Ale, and we do need a spot to field Diego in behind the striker(s).
We can't play straight 4-4-2 with Diego being our most talented player, and with our glut of central midfielders we need to fit them somewhere. Sissoko, Melo, Marchisio, Poulsen... all strength up the middle. So unfortunately the 4-3-1-2 IS our most suited formation looking at our squad.