While i do see a benefit of isolating diagnostics from treatment if you started evaluating outcomes, done on its own it seems like a bad idea:
To diagnose well you need to know which things are relevant for treatment, which means learning most of same knowledge as the treater would have.
Information transfer between humans is time-taking and lossy, so the Treater would most likely have much less knowledge to base his treatment on than the Diagnoser, leading to increased risks of wrong treatment (for a practical example if the initial diagnosis was wrong, original diagnoser would be in a much better position to notice this when getting more information during treatment than a Treater who did not see the original data).
Also teaching quality will be much worse if teachers are different people than those actually doing the work, a teacher who works with what he is teaching gets hours of feedback everyday on what works and what does not, a teacher who only teaches has no similar mechanism, so he will provide much less value to his students.
On doctors:
While i do see a benefit of isolating diagnostics from treatment if you started evaluating outcomes, done on its own it seems like a bad idea:
To diagnose well you need to know which things are relevant for treatment, which means learning most of same knowledge as the treater would have.
Information transfer between humans is time-taking and lossy, so the Treater would most likely have much less knowledge to base his treatment on than the Diagnoser, leading to increased risks of wrong treatment (for a practical example if the initial diagnosis was wrong, original diagnoser would be in a much better position to notice this when getting more information during treatment than a Treater who did not see the original data).
Also teaching quality will be much worse if teachers are different people than those actually doing the work, a teacher who works with what he is teaching gets hours of feedback everyday on what works and what does not, a teacher who only teaches has no similar mechanism, so he will provide much less value to his students.