I'm not really an instructor, but, I do help my kids when they are not around Al, Klem, Stan, etc., so maybe my comments have some meaning.
I've had a W10 for over a month now, and taken several videos of casting. I have found the videos to be the BEST way to identify faults, and communicate them. The video is particularly potent when combined with pictures of proper technique:
After a fault is identified, the video can be viewed by scrolling slowly through, and perhaps stopping at a key part. The video/picture can be compared with a picture of proper technique, as, for example, from Simon's book. Here are some of the things we noticed and/or communicated recently. (Our first casting sessions in many months, and most of last year was a bust for the kids because of injuries, so maybe they were off form...)
Me: Fail to raise the hands/rod tip as the d-loop is forming, with the potential to increase line stick.
Olga: Rod tip path during d-loop formation is nearly parallel to the water, so that all the lower leg can hit the water at once.
Roman: Stroke is too short because of creep.
My experience is that the use of a digital video for casting analysis is great!