Yes, MCAT is a joke for Singaporeans in terms of the difficulty of the questions. But when Singaporeans to do MCAT under time constraint, that is another story. Singaporeans are trained to do extremely difficult questions in ample amount of time but not easy questions under very limited time.
Please provide evidence or stats showing that the quality of the students in Duke-NUS has been declining over the years.
Please do not compare Duke-NUS and American medical schools in the American context. If you really want to compare that way, I can tell you that Duke-NUS graduates are consider FMG in USA and residency match rate for Duke-NUS graduates will be even lower than those from American DO schools if they want to practice medicine in USA. If you want to practice in USA, going to a DO school is indeed a better choice.
You can always pay the full fees (without government and MOH subsidies) for Duke-NUS education, after that you will be free from the service bond. No one is forcing you to come to Duke-NUS, everything is made clear to you before you sign the service bond contract. Your European servants example is a very poor example.
Singaporeans are trained to do extremely difficult questions in limited amount of time