I took classes in my PhD where we would read 4 papers a week, which is close to one a weekday. Some of the papers were very theory-heavy, when those came up you would spend half a day just reading.

Of course, for a seminar class, you do the strategic thing and read enough to not be caught flat-footed during seminar, and to come up with a few salient points of discussion.

I looked some at the papers read for this project and they seemed to be very systems-heavy. Having taken both theory-heavy and systems-heavy seminar classes, the systems-heavy seminar reading loads were much easier. You could probably read 5-8 systems papers a week, to comprehension, if you really wanted to.