DFB-Pokal games, like all internal cups, are different and that is the reason why I believe Leverkusen will win this game. At more than 2.something I believe it can be considered like some sort of gift from the bookies: I will play my chance on this single game. And we will be basically betting the opposite 
Agree with you in the point that such cup matches are special and have their own rules. I am very curious how Bayern will react after the surprising defeat. Leverkusen today has the opportunity to create a surprise similar to Gladbach.