Wrong mentality. Bayern played like they were 5-0 up and simply didn't care at all until they realized Arsenal can still cause them troubles. That lesson was well learned, Barca will agree with me too.
Other option would be to go with an extra man in midfield and play more like 4-3-3 with Kehl, Bender and Gundogan in the middle with Reus and Błaszczykowski off Lewandowski.
Klopp doesn't seem that inclined to change shape, though, so I'd expect Grosskreutz to play and for it to be 4-2-3-1.