@Prosper, here's the thing. When you get to an advanced level of skiing, you have a set of ingrained movement patterns that you use in your skiing. The reason they are there is because they worked for you. And depending on how long, and how often, you've practiced those movement patterns will dictate how ingrained they are.
Some of those movement patterns are likely dead-ends that are frustrating your efforts to become a more accomplished skier. And those movement patterns are likely embedded in your belief system about how to make a turn, what biomechanics are involved, what the physics are that govern ski performance, as well as your tactics. And all of that is specific to YOU -- it's not only YOUR ingrained movement patterns, but YOUR anatomy, YOUR beliefs, YOUR tactics, and YOUR experience.
At the high levels of skiing and learning, it takes a lot of time, study, practice, questioning, and feedback to make significant changes in your skiing. The process is most assuredly NOT easy. And while some might be able to do so on their own, success of self study and self instruction is NOT likely to be successful. Why? Because an external frame of reference is not only most useful, but often required.
How many times have you been asked to perform a task while skiing, thinking then that you performed it, only to find out you did not? And how might one who is attempting to take their skiing to the next level (which implies that the knowledge of what's deficient in the current movement patterns, what would be more ideal, and what the best method of addressing the gap with the least effort and most reward is) be able to accomplish that task?
Group lessons are not private lessons. They are specific to the issues in the group, not the individual. And while some instruction in a group session may provide feedback to the individual, the lesson almost certainly will not be tailored to any single individual -- it's just unlikely that everyone needs exactly the same thing at the same time. Or masters the task at the same rate.
This is why, at the higher levels, private lessons are much more efficient than group lessons. They are also much more expensive. My own development path used group lessons for more than 10 years. But in the end, what made the difference was private lessons with a coach whom I had developed a relationship. And my group lesson experience was in a "lesson club" group where I skied with the same instructor every week -- a better experience than random group lessons that I've found are good usually for social fun, but not for deep learning.
So, my advice for you is to find a coaching opportunity. I realize most people cannot afford private lessons, and (IMHO) it isn't just a single, or even a few, private lessons that will make the difference. If you aren't one fortunate enough to be able to think about a long-term private coaching experience, then look for an opportunity to find a coach in a group setting.
That's why I think finding a masters racing program would work for you. You will have coaching from a consistent source. And racing has a focus on technique, and a measurement protocol to assess progress: your time.
A race camp would also be a good option. A lot of instructors here in Aspen go to the Rossignol race camp at Mammoth the first week of May. Very high level coaching, and you'd have a lot of very experienced instructors in your group (many of whom are examiners in PSIA as well as coaches in the USSA) around you to help out. Plus Mikeala Schiffrin is there running gates next to the training for inspiration.
Just my $.02 from a fellow traveller who has been remaking his skiing for the past 15 years.
Mike