Thanks again for all the responses. Here's my experience:
I kept my class diagram and component diagrams simple. I only had about 15 classes in my class diagram. I submitted multiple component diagrams, each containing about 4 or 5 components. I am not sure why I got such low score on the sequence diagrams, because I actually spent more time on the sequence diagrams more than anything else. However, as I was examining the sequence diagrams, I was able to spot some flaws in my class and component diagrams (or the whole design for that matter). So all is not lost. I only wish I explicitly addressed some of the issues that were asked in Part III, that way I would not have to worry
. My "assumptions" section did not cover a great deal of details (I did address some of the design issues), specifically, I did not mention anything about the use cases (maybe that's why I got low score on the sequence diagrams).
Overall, my suggestion is: keep things simple. But I understand different testers may have different scorers, so your mileage may vary (no pun intended).