Hey Chris,
Multi-practitioner business models have the option to either:
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Promote the practice + promote the practitioners, or
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Just promote the practice
If you go with the first, the main thing is to be sure that each practitioner has a unique landing page on the website (to which his/her citations link) and that each has his or her own phone number (separate from the practice's main phone number). Taking these precautions should normally prevent any issues with merging, but I am not quite sure what you mean about duplicate reviews. Are you saying that the patients are posting a review for the practice and then posting the same review again for a specific doctor? A little clarification on that might help.
If you go with the second option, then, yes, you can attempt to get rid of citations for the practitioners, but, because you are talking about a medical practice, it's very important to dig into Google's history with not closing doctor/dentist duplicates. It may be that the Yext rep with whom you're communicating is unaware of this. Note Linda Buquet's remarks on this previous Moz thread regarding this: https://moz.com/community/q/dental-practice-google-and-dentist-personal-google
Hope this give some good food for thought.