Bayern fans are scared and getting excuses out of the way ahead of time.
Remember bayerns massive catastrophic crisis is a big deal. When they beat us before it doesn't matter that a player and manager had cancer, we had several injured players etc.
As far as I remember you had almost the entire squad. You could argue that Messi was not 100% but he was there playing. That game was won on tactics, Bayern had it right and you not. I agree that the result 7-0 can happen and did not reflect at any case the difference between two teams, but who is excusing now? Get over it and focus on the upcoming game. Scoring 0 goals in 180 minutes against Bayern or any team, hardly gets you through no matter what excuses you have. If it had been a close result then yes you could argue that you missed this and that. But the truth is in 2013 Barca got totally outplayed.
Same happened to Bayern last year vs Real. You could say that 5-0 is a demolition bla bla, although the result did not reflect the quality difference between these teams. What happened is that Pep had it wrong and Ancelotti had it right, they outsmarted our tactics and were ruthless. It hurts but that is football. Yes, we could also say that these were the same players from 2013, or even stronger then the team that outplayed one of the most expensive Madrid team of 2012, that Pep was mourning the death of Tito and was not focused, as that guy wrote on his book etc, but at the end Bayern didn't deserve to go through based on what they produced, same goes for you in 2013.
I don't think players will approach this game as a revenge, although they will kill Bayern if such possibility arises during the game. Let's see. At the end, despite we miss Robben, Ribery and Alaba, we are not preparing ourselves for any loss or catastrophe. So no excuses. Even if we are weakened by injuries I still believe Bayern have all what it takes to do harm, At the end it will depend on tactics and physical form of players on the day. And that is to be seen. The pressure is on you, as the heavy favorite. But please name another team in the planet that has such a positive record against you in CL, and even won 3 out of 4 clashes in Nou Camp. So treat Bayern with more respect or discount it at your own peril.