There never is a "good time" at the passport office in Düsseldorf. I've heard every excuse under the sun from them for delays in processing passports but after you contact them they seem to be magically able to get you to the top of the pile and process it quickly. The did
announce likely processing delays for w/c 4th May, but it's now two weeks later so no real excuse. Their premium rate enquiry number to find out any information costs €1.79/minute so even contacting them is not cheap. Last time I had a passport renewal there the cost of the passport actually increased between my submitting the forms and them being processed, so they called to tell me it would cost more. When I asked why the charge was higher they mumbled about the prices being tied to the £/€ exchange rate, but this was at a time when sterling was weakening so they should have got cheaper!
I suspect, at the end of the day there is only a small staff handling a lot of work - the folks in Düsseldorf now process passport applications enquiries from Austria, Bosnia & Herzegovina, Bulgaria, Croatia, Kosovo, Macedonia, Montenegro, Serbia, Slovak Republic and Slovenia which will be quite a few ex-pats.
If you DO need your passport urgently and they are ready to dispatch it, they'll surely tell you that the post is slow and might delay it further but they can recommend a courier firm around the corner from them who will get it to Munich overnight for a paltry €40