Yes what you say is right playing a 4-1 (DL,DC,DC,DR,DMC ) or 3-1( DL.DC.DR.DMC) old sweeper style is needed, with that formation the back four or three could drop back and hold a line maybe 25-35 yards out and rely on the defencive midfielder to offer support!, they could still play the offside trap but at least they would not be so far away from goal if they got caught out, plus the space behind them and the keeper is only half what it is now so the opposition strikers would not have anywhere near the amount of space to exploit and this would also give the goalkeeper more chance of coming out and reaching the ball first!. I f we did play 3 at the back then we could play 4 in midfiled, keep the wingers out on the flanks and still have 2 central midfield players like Erriksen and Siggurson as play makers and support men for the two strikers, this to me is the way I think we should play.
My team with what we have now!.. Formation..1-3-1-4-2 or 1-4-1-3-2!.
1-3-1-4-2..Lorris, Rose,Vertonghan, Dawson/Kabul, Walker, Sandro/Dembelle, Chadli, Erriksen, Siggurson, Townsend, Adebayor, Soldado.
1-4-1-3-2... Lorris, Rose,Vertonghan,Dawson, Walker, Sandro/Dembele, Lennon, Erriksen/ Siggursen, Townsend, Adebayor, Soldado.
These two formations in my opinion offer our best balanced team, it needs to be played regular and as the back three/four get used to playing deeper they will feel more comfortable knowing they are not leaving half a pitch of open space behind them for teams to exploit, plus it makes the long ball over the top alot less effective aswell because the defence have more time to back track.