I can see your concern, but i don't think Bertrand, Eardley, giddings, Lomax or even Stam are equipped to deal with long diag balls over the top! For me only Thomson could cut out that. But i think apart from this weakness, Bertrand, Giddings and Eardley have on evidence done a reasonable job defensively this season and i'm sure Crossley would vouch for that, as he hasn't exactly been 'mowed out' over the last couple of games!
I think most teams will struggle with a 50 yard diag ball over the top, because if you are coping with that then imo, you are too deep anyway!! Especially at home!