1. The feeling of hecticness is absolutely much better than before. However, the underlying mechanics of gathering and depositing stardust still is a bit flat. Having more hazards in the map and/or from special enemies would go a long way to mix things up and require more skill and focus from the player when they move around.
2. It's hard to say, though the asteroid and sun towers feel a bit samey apart from their appearance and elements. That's not really a huge problem though, as getting different elements out there is an important mechanical difference in its own right. I'd love to see more variation in the future towers now that there's a way to get each element, however.
3. Not really, an in-game text prompt explaining the system would be quite useful. Also, after being told how the system works by one of the devs, I feel like the system could benefit from being flipped. Instead of enemies resisting the element they are, they should resist everything *except* their element. That way you will need a diverse spread of tower types, as currently you only need two elements in order to cover each other's weaknesses.
4. The game flow is good, although sadly there's not much in terms of progression between the levels, they're all quite similar to one another with the lack of hazards and other special environment features besides the colors.
5. The UI is great right now, good job on the implementation for the auto-play button.
6. See #3.
7. The multi-tiered system feels very good!
8. Absolutely, it seems to be at a good balance right now, slow enough that it doesn't entirely remove the need for collecting stardust manually. It may or may not need a slight cost increase though, I'm not sure.