The way I see it, apart from Iestyn being an average/poor coach, is if you're going to have a squad with some top class international players and x factor players with real quality, the rest of the team need to be very competent and confident in defence if nothing else.
Wigan and Saints have a squad full of players who are committed and competent in defence and also a few x factor players to break the line and create tries.
It's no good having Locke, Rangi and BJB when you've got Mason Caton Brown out wide.