I agree with most of your points Metaphor...you can't substitute for a really good eye and development coach/mentor, and perhaps we are very lucky to have some of the best in the CSIA help us but maybe OP doesn't have the access or afford the prices these guys command?
I have found instructional videos from DVDs and clips very helpful and learnt some drills never shown to me by my current trainers. You certainly can learn from DVDs and clips, especially if you are a visual learner and can get video of yourself to compare. The most important thing is WHY? and HOW to do it properly. The CSIA drills package or the clips of the girls don't explain why, so pretty useless, unless you know the purpose, HOW it will develop your skiing and when it applies to you. The Warren Smith clips are very good, although simple as they explain why and how, and has good biomechanical basis for it, but then you need to know what you are working on first....
Feedback junkies rarely get anything new. What we are working on would hardly change overnight, especially at the higher levels and if OP knew what that is, he can certainly benefit from getting tips from videos....but you are right it's no substitute for a good instructor's feedback.
The advanced DVD previews I have seen online are intermediate.
What do you mean by this? What would your like to see in them? What do you aim to learn from DVDs? What do you hope they will add to your skiing? Don't forget drills need not to be difficult or complex to be effective as long as they develop the right 'feelings' and movement patterns that apply to you.
BTW I've got a couple of Richard Berger's Videos form an Austrian friend, it has some great stuff but I can't understand German or Japanese :( Has anyone found any in English?