I think that yes, it is healthy to have expectations of Dr's, Dentist's etc. You are putting your health in their hands and they are responsible for making decisions that could impact your life. So yes, I would say that an expectation for a Dr., Dentist, Therapist etc is that they act with your best interests in mind, understanding that there is always room for error.

The way I look at it, if you hire someone to plow your driveway, you expect to be able to drive in or out of the driveway without getting stuck. If you hire someone to fix a leak in your roof, you expect that the end result will be roof that no longer leaks, and that looks good too. So yes, absolutely, any professional that deals with your physical or mental health should expect to be held to expectations of some sort.