Whooooooa whoa whoa, that’s now how any of this works. It’s still three total cube powers - you can just pick those 3 from any category, instead of having to have one from each. If I need to make this clearer for future versions of the patch notes, I absolutely will! Apologies for any unintended confusion.
Yes and no. We have a lot of work to do on both Demon Hunter and Necro, and we’ve known this for some time. But that work also takes time (as does the art assets related to their upcoming sets; sometimes art happens faster than design necessitates and vice-versa). Part of the reason the order of class sets have come out in the order they have is because the art, rigging, and implementation graphically was ready first.
There has been no change to Spirit Barrage or its interaction with Ring of Emptiness. However, utilizing Ring of Emptiness with the new set might be a bit challenging, in terms of juggling which skills you want to use to benefit from it.
We’re going to see how it plays out for now, but we’ll keep an eye on it throughout PTR testing to see if any changes need to be made. As always, we’ll prioritize the health of the game first. 
Great question!
This is a very astute observation and accurate assessment. Balance does take time, as well as a lot of research. We’re also adding new content on top of that with the new sets. So it’s going to be a bit of back and forth, and it’s going to take time. We’ll do our best to always continue moving forward, as much as we can at a time.
If that’s what you really wish, I can accommodate. I understand your frustration; it’s hard when you don’t have stuff for your favorite or preferred class coming up, especially when you’re really passionate about it. Barbarians went through this for many patches before we got to them, and Necromancers haven’t had significant changes since they were added to the game.
We are addressing as much as we can, as fast as we can. If that incenses you beyond the point of wanting to participate constructively and help us start planning for that future (rather than being hostile and attacking people needlessly), I’m more than happy to fulfill your request. For now, though, I think you just need to take a break to collect yourself, and probably outside the confines of these forums.