As you said "Dr. Mr. Somebody" is wrong in English as well as in German.

If you take it even further you would need also to add postfix titles to the list as most of the academic titles in the US in England would be stated postfix, right? "Mr. Somebody, Ph.D" or "Ms. Someone MD".

I guess nobody looks to close on those titles anymore anyway, there are so many different forms even in the classic "Dr", "Dipl.-something" etc that it hardly justifies to put down a complete list and hope it is correct in all parts of the world.

As long as you can clearly identify the passanger on the ticket, who cares?