The turn around from Bayern has been incredible though, as is looking at this list to get a good idea of just how epic they've been.
http://www.statto.com/football/teams/bayern-munich/2012-2013/results
I do like statto with different colours for the results you can really get a quick feel for a season and form of a team.
Bayern are currently one point off their total from last season, and 10 points ahead of Dortmund at the same stage last season... who are themselves 10 points behind where they were last season.
I think in large part you have tiredness playing a part and certain players won't have their best season every single season, but they probably have also favoured the champs league, trying to make that adjustment to yearly European football. Last year they got a bit spanked in Europe while focusing on the league, to really do well in the champs league you have to rest players sometimes before/after champs league games and throughout the season to keep the squad fresh. I think this season is their learning how to cope with Euro football season, as such their league form has suffered, but Bayern have just been incredible, 4 games total they've dropped points in, absolutely astonishing league form.
http://www.statto.com/football/teams/borussia-dortmund/2011-2012/results
The two back to back losses had an away champs league game in the middle and the back to back draws later on had a champs league game between them, after they were out of Europe they dropped 4 points total in two games.
http://www.statto.com/football/teams/borussia-dortmund/2012-2013/results
This year no where near as good but most of the poor runs of form or dropped points come just before or after champs league games, or whenever champs league games make for a busy couple weeks, I cba'd to check but I'd just say I wouldn't be surprised if they rested players more for league games to have their strongest for Europe, and their Euro form compared to last year is night and day.
A better champs league run will mean more cash to build a stronger squad for next year though, another 10mil, another 2-3 players they can sustain wages for.