De Jong is perfect in a midfield 5 with a box-to-box player he can just pass it to after a tackle and then a creative midfielder who the box-to-box midfielder can work with to create chances. In a 2 man midfield, because his game is so lacking you would need him alongside a Gerrard/Kaka ability type player and we don't have one.
Although, having said that, because of the talent we have already going forward you are able to play De Jong in a 2 man midfield against the lower half of sides and still pick up a result. Our midfield was a serious weak spot last season and Barry offers that little bit more for me, he is always available for a pass and to spread the play and alot of his tackles and "Clever fouls" go un-noticed because they aren't flashy and agressive like De Jongs.