The core problem is what you've identified in your blog. You assignments don't explain many core concepts that students struggle with, they move WAY too quickly through concepts, and there's no coherent sequence. For example, in the middle of the "Conditionals in JavaScript" assignment/tutorial, you throw in arrays and loops. Both are MUCH harder than conditionals.

Zed Shaw, on the other hand, does a marvelous job of not covering concepts until the prerequisite knowledge is already in place.