IMO, if you're studying 8-10 hours per day every day in addition to going to lecture, something is wrong, but then again I'm not striving for a competitive specialty so I'm perfectly content with scoring middle-of-the-road on exams. Everyone figures out their own system, and the important thing is to not compare your study habits with someone else, because that person thinks and learns differently than you.
I'll usually study/listen to lectures 3-4 hours a day and then ramp it up as the exam gets closer, usually like 12 hours/day the weekend before the exam.
It's not a waste of time if you're an auditory learner. I'd say about 1/3 of my class regularly goes to class, just because they learn best by hearing information. I'm a visual learner, so hearing things does nothing if I'm not writing things down, writing it in my own words, or drawing diagrams/flow charts/making spreadsheets. I don't usually go to lecture unless it's not being recorded (when there is patient information/patient videos) or unless it's a lecturer I particularly like. Sometimes I don't even listen to the lecture because the notes we're given are so detailed + images that there's no additional info in the lecture.