I'd like to add a few more pieces of UI feedback, or rather, improvements I would like to see, here. Note that I am not a premium level backer but I have been watching streams of the game being played.
- Enlarge the scrollbars on the side of scrollable panels based on the percentage of content visible within that panel. For instance, like the web browser you're using to view this very page! I really dislike scrollbars which use a fixed-sized dot as it gives me no information about how much the panel will scroll if I move a certain distance.
- Make the "End Turn" button more visually impressive and important, similar to how it is treated in games like Civilization or Total War (e.g. make it a big hourglass icon or something). It currently looks like it was sort of just added in hastily, despite it arguably being the most important interface element in the battle screen UI. It could also do some cool animations when it's the enemy's turn or something.
- There appears to be very little gratification for winning a battle. I find the end of battle screen to be a bit ... underwhelming? It just sort of pops in when you win or lose, rather than there being some cool "Massive Victory!" text/animation and corresponding victory music (think of something like Dota 2's victory sequences).
- I feel that the big "LEVEL UP!" that flashes over a hero at the end of battle looks kind of hokey.
All this said, I don't know if the UI is complete yet, or if there is going to be another pass of polish on it.
One thing I wish the UI did have, is art for random events, like in Crusader Kings 2. However, I understand that the game probably doesn't budget for this.