When did you get that CASPer cutoff e-mail from Dalhousie? And to answer your question, no. CASPer has a really strict format and a massive time constraint. The biggest thing about MMIs is that they are assessing oral communication whereas CASPer doesn't. MMIs involve actually talking to someone, not frantically typing on a keyboard to answer 3 open-ended questions in under 5 mins. As long as you're comfortable talking to interviewers and ready to discuss anything they might throw at you, I wouldn't let your CASPer score be of concern with respect to the MMI or a regular panel interview.