The notion that Barca is off form at the moment is as false as declaring Messi being off form after not scoring in 3 games.
We have played different formations and players until now. Players like Xavi, Iniesta, Villa and Pedro are rested a lot. Only attacking player who is playing every game at the moment is Messi. Even though Xavi, Pedro and Iniesta didn't play in our 2 last matches and Villa was subbed in one and didn't play the other we won 4-0 and 5-0.
For many people it might look like we are off form at the moment but i simply feel that the fluidity in our game seems not as great as last season dur to the fact that Thiago, Fabregas and Keita are getting more minutes and Xavi and Iniesta are rested a lot. In addition, Pep is playing 3-4-3 formations in some games to see how it will work.
During Guardiola's reign, we have always peaked in September and then our form dipped through Jan-february. I believe Guardiola is resting Villa, Pedro, Iniesta and Xavi as much as he can now because he don't want to see dip in form this season. We can't simply afford to loose our form during January and February because Real Madrid is really breathing in our neck and we can't afford any slip up.
Alves, Xavi, Iniesta, Pedro and Villa are the players that do most running in this Barcelona side. Last season during some games Pedro and Villa looked very tired. Xavi and Iniesta are constnatly running in the midfield and they too gets tired if they are played every game. Alves is the only player who seems unaffected of all this running. Therefore, my view is that Pep is resting Villa, Pedro, Xavi and Iniesta intentionally. He wants these players as fresh as possible when the business end of the season comes.
Therefore, my answer to the OP is, even though we are looking not as brilliant as last season, we can pick up our game immediately. If we are to play City next week our starting 11 will be the exact starting 11 we had against ManU in Wembley. I don't think your team is prepared to take on us yet.
You have a great team at the moment and you are playing brilliantly. But don't forget this Barcelona team is the same team who comfortabely beat Manchester United 2-0(it should have been more) when they had players like Rooney, Tevez and Ronaldo. EPL is completly different from CL, and for some reason English team finds it very hard to play against continental teams.
So my take on this is, you should first beat Bayern Munich before you can even think of winning against this Barcelona team. If you beat this Bayern side, i will be seriously worried about your team but until then i still believe we will be too strong for you.