Without counting the waiting time, I'd say my doctor spends about 5 minutes per issue. Since I loathe going to the doctor's office, I generally have more than one issue by the time that I get there, but this last time I went, I got a knee examination, a script for physio, an X-ray and a surgical consult all in less than ten minutes. Prescription renewals at my family doctor take about a minute. The nurse who takes my info at the beginning probably only spent two or three minutes assessing me. He's my family doctor, and though he's working from a larger office now, there's no real difference in wait times than there would have been at his old one-man office.
I always know exactly what I'm going to say when I go to see him, though (and can usually tell him what I have), so I imagine that it would take a lot longer if I didn't walk in and say "I have strep throat, these are my symptoms, please send a swab to the lab." My mum did the same for me when I was a kid, so that's just how I deal with doctors. He takes it very well, but there are some doctors who don't like being "told." Those ones usually make much longer examinations, probably just to piss me off.
I wind up at the doctor's at least four or five times a year for different reasons, though, so I don't mess around. Usually about two visits per year are for bronchitis/a chest infection. I won't go until I've waited at least two weeks to see if those resolve themselves, though, so they're usually pretty bad by the time someone forces me to go. I know that that's nothing compared to some who take weekly trips to the doc, but it's often enough that I am very glad to live in Canada.