I've read those cases many times last year. Don't worry so much about them. What I've noticed in common among the dismissed cases was the couple providing contradictory statements (ex. husband says they first met at airport, wife says they first met at her house) or the couple keeping silent/providing vague responses to questions being asked.
As long as you go through your GCMS notes + failed interview to see what your "red flags" were and then work on providing good explanations for them, you should do just fine.
I think part of the reason for the supposedly high rejection rates on the Canlii website is because Vietnam is a high marriage fraud risk country, so not only will you get lots of successful applicants, but also LOTS of fraudsters, therefore you will see lots of refusals on that site.