Most online learning courses aren't particularly challenging. There are exceptions (Coursera's Probabilistic Graphical Models, MitX's circuits etc) but most courses seem watered down for online consumption.
One big flaw I can see is that there is no way to do proofs or otherwise handle theory in the problems sets and assignments. This limits exploration in depth, particularly for math/science/CS.
More often than not, I find being able to share visual information gets thrown at a side-tool that the community adopts for this specific purpose. Something like Google Docs (drawing doc) or some whiteboard app.
What, if any, efforts are made to find a solution like this (or related)?
One big flaw I can see is that there is no way to do proofs or otherwise handle theory in the problems sets and assignments. This limits exploration in depth, particularly for math/science/CS.