I understand the situation that you found yourself in, but might I respectfully submit that just that sort of oversight is just what gets experienced and capable divers killed.
I have never asked about the qualifications of the other students in any of the advanced courses I have taken. I believe this is between each individual student and the instructor. I can't remember the requirements for starting advanced trimix through TDI, but it would be natural to assume each of the students have met them, are qualified to be there, and thus qualified to dive to the level of training once they have sucessfully completed the class.