Hi davsav89,
I think with WHU, Mannheim and HHL you have covered the good German B-schools pretty much.
You mentioned that the reason for a German B-school is that you want to enhance your German language skills. If the language is your major reason, you may want to consider that the german-speaking region is bigger than Germany itself (you specifically asked for b-schools in Germany). Austria and Switzerland also might have good b-schools.
At Mannheim admission depends on your point score, the computation is explained on the university websites. In german-speaking forums there is plenty of discussions, with which pointage you can be expected to be admitted.
At WHU, admission pretty much depends on the admission day. With your profile I would think that you would be invited, but how it goes from there is difficult to assess without further information.
Also you may want to keep in mind, that Mannheim on the one hand is a huge, public institution, whereas WHU (and HHL) are (rather) small, private institutions. This has implications on fees and the day-to-day situation of studying.
If you want detailed statistics on the MiM programs, I would suggest to look closely into the Financial Times (FT) MiM 2014 ranking data. While they rank the programmes, I think the rank itself is basically meaningless for an individual (would you put the weights exactly as the Financial Times did?). However, the financial times offers a pdf-file with very detailed information on the different parameters of the various programs (and also on the weightage the Financial times used to come up with their rank). Personally, I find this detailed statistics to be pretty useful.