This is one of the reasons why DCL and other cruise lines hand it all over to local tour operators, and these, generally apart from DCL characters are all exactly the same.
The tour operators, know what an statistically average cruise ship books, and will plan to that, they can add a coach or tow or three, or drop one, they can add cars to the train.
But there is a limit, and as the Magic will have a higher percentage of USA travellers on it, they will I think book more shore trips, 1/ The Med proved this, I went private as i am European, but 2/ People from say London, can get to Berlin quicker and cheaper by plane, than from the port. So Europeans would be less inclined to book Berlin, but people from USA, more inclined as they cant go there for a weekend.
I hear you, but this gets me back to considering doing the whole thing on our own. In addition to the SPB Tour company quote of $880 for the four of us with a pick-up in Warnemunde, the German tour company quoted 850 euros for a round-trip tour, which is also cheaper than taking Disney transport and then hiring the tour company. $800 for the four of us to get on a bus seems, even by Disney standards, really out of whack.