I'd advise getting to know the professors styles for each class. We had a couple 2nd and 3rd years take a Real Analysis class similar to what you described and they said averages for exams were around 20-30%. I've had Russian math professors that were completely fine not giving out A's to an entire classes. There's a lot of idiosyncrasies in grading styles in math classes. Also, if you're in a Phd program there's nothing that would preclude you from taking such a math class.