The chance that a DM candidate would achieve excellence in every aspect of the DM course, on their first attempt, is highly unlikely.
OK, let's look back on the history of dive instruction;
Let's just say all recreational certifications descended from the LA County Lifeguard program.
Let's just say that PADI "dumbed" it all down to the "too easy" certification courses we have today.
Let's just say becoming a PADI instructor is so easy that lots of people who are not really graceful (or even comfortable) in the water are now MSDT and higher.
I'm of the opinion that if you can't show excellent mastery of the PADI DM dive skills in a week you should seriously reconsider whether you are really cut out for DM certification.
And the book/test; read the book, do the exersizes, fill out the knowledge reviews, pass the test. It's designed so an 18 year old without a high school diploma could pass it.
Seriously, the people clamoring for 6-9 month DM programs fall into two catagories from what I see;
The first are all the people who got their DM from some ex NAVY Seal, and think everyone else should have to do the 50 push ups in full doubles dive gear.
The second are all the dive shops/instructors who make DMC's part of their bottom line; slave labor that actually pays them for the privillege of being slave labor.
PADI DM is so easy, if you can't do it in 2 weeks I don't think you should!