Online discussions in some ways they are better than traditional face-to-face synchronous discussions. They are more equitable, giving everyone time to think, and leveling the playing field for intro- and extroverts (who are always guaranteed to win in face-to-face discussions!).
In content-heavy courses, across all levels, lecture is still the main method of content delivery. The challenge is: once you have a reasonably good lecture (say, 30 mins. long). What do you do? How do you transform your video lecture into a productive and effective learning activity? There are a few options, but this one is probably the easiest and best of them all.