1. He was believed to be a doctor. 2. He was believed to have been a doctor. #1 people thought he was a doctor...(was! Maybe he died now, or moved away). #2 People thought he had been a doctor (at one time) but he's not a doctor now.

1. He was believed to be a doctor = he is known to currently be a doctor/is presently a doctor. 2. He was believed to have been a doctor = he WAS known to be a doctor (past tense) so he is not a doctor now/anymore, but used to be.

*The kind of sentence "People consider/think/believe/...that he is..." has two forms of passive voice. -He was believed to be a doctor=People believed that he was a doctor=It was believed that he was a doctor. *When your thought related with the previous action,"To have past participle" wil be used. -He was believed to have been a doctor=People believe that he was a doctor=It is believed that he was a doctor.

He is known to be a good doctor (We say, now, that he is still a good doctor; an active practitioner.) He is known to have been a good doctor (We say, now, that he was, in the past, a good doctor; he may be now a retired person.) @http://forum.thefreedictionary.com/postst12388_-to-be--or--to-have-been--.aspx