Is it really too "hard" to perform rigorous statical analysis? Why can't you factor in patient genetics + background + circumstances to come up with some expected chance of success for each procedure (in fact, isn't that why doctors have such detailed patient histories?). Isn't it the doctor's job to estimate and inform the patient of the expected outcomes?
Doctor's historical success rate exceeds expected success rate on average => Good (or lucky) doctor.
Doctor's historical success rate exceeds expected success rate on average => Good (or lucky) doctor.