Of course their wingers will cause us serious harm, but don't make them better than they are. Just like Lahm and Alaba shouldn't be overestimated - Lahm in particular, who's not even close to the player he used to be. Alaba, while obviously class, is no demigod, and was repeatedly humbled against Juve. Nerman and Messi should cause them loads of trouble.
About their weaknesses, then I think it's obvious that old man Alonso crumples under heavy pressure - perhaps the position where we completely outclass Bayern. That and counters.
I know Bayern were weakened when we faced then last season, and if we face them again, it will most likely be a 50/50 tie, but this notion that they have more means to hurt us than we they, is silly. Again, let's not forget that they're extremely lucky to even have qualified for this stage of the tournament. A Juve team without 3 of their perhaps most important players, should've put them to the sword, but was only foiled by bad luck and the referee...