the problem in my opinion lies with opposition having deeper lines than the ones that barcelona faced in the former season. deeper defensive lines doesnt allow our forwards to actually get behind their defenders and be in firm control to score a goal. secondly, it has cause our midfield to spread out more causing the tiki-taka football to not be as efficient as it probably can be.
the teams that have fared to play a higher defensive line than us have been utterly destroyed like zaragoza. the only way to remedy this is to make our attackers come closer to midfield allowing xavi to send more through balls for players to run after. our opposition has evolved their tactics to benefit them and hence, players like henry are finding it hard this season... and if eto'o had stayed here... we would have seen a similar demise.
of course, this is all a pure speculation but a winger would definitely help us if the system doesnt get changed.