Well, City create the most chances and have the most possession. Only team that is playing positional football at its best atm. The rest just stay back and play on transitions for large portions in big games.
Bayern and City are the least dependent on individual players' output. Madrid is the 3rd least dependent, Barca is the most dependent, as in without Messi, or him contained, more than half our attacking capabilities go out of the window. We are less structured in how we go forward than all others mentioned.
In short, Barca's attacking plan is as simple as to find Messi and from there he will dictate what to do and where to insist. Once in a good position, score-wise, go with a low block (2 banks of 4 with Messi and Suarez having limited defensive duties), play on the counter with Messi in space. Everything is about Messi.