English seem like the largest issue, because the system would need to be able to understand an essay to grade it and provide feedback. The other issue is intro classes are setup to go over material with the expectation that people will form study groups if they don't understand it. Which in many ways is punting the issues of education back on the students.
P2PU has an implementation (clumsy, at this point) of the "study group" concept -- but there's nothing about learning online that makes it impossible to collaborate with fellow students, right? I agree it's a problem, but I think it'll be solved sooner rather than later.
As for the English example, you'd probably run into that problem for all types of writing-intensive courses. That seems like potentially a major gap in this entire model of learning. Multiple-choice and defined-output problem solving sometimes just can't cut it...
