I'll split feedback into two sections: UI changes and new mobs
This is based on my opinion and is likely going to be different from what you think

UI Changes:

• I like the weapon change wheel, but I think it is a bit unnecesary. When alchemer switching it is annoying. Please make it toggleable
• I hate the vial icons and the vial slots with a passion. They're fugly and should be redesigned into something less shiny. It is completely out of place with the rest of the game.
• The health and shield bars are nice, but the shield bar resizing each time you shield is annoying and unnecessary. I also don't like the new art style for the health bar. The % is ok, but overall I prefer the old/current health bar.
• I don't like the fact that the crown and energy displays are hidden unless we have the arsenal tab open or are buying something. At least let us have the mist bar open so we can see how much mist we have.
• The knight icon in top left is quite unnecessary. Make it do something, or let us toggle it off.
• The interface that opens when you stand on an elevator is different but nice. I would like an option to toggle it back to what we currently have though.
• The bars for gear tooltips are fugly. Change them back please.
• The monster health bars are nice. not too simple and not too fancy
• No matter what I did I couldn't get the box that was seen in the top right with the monsters weaknesses etc up. Did you remove that?
• The party health display is nice, and I like the fact that you can see if they're inflicted with statuses from it as well.
• Overall, I think the new UI is nice, but a couple of changes should be made. An option to toggle the old UI back too would be nice.

Compounds

• All the swarm monsters need a universal health buff. Seriously, they need to be able to take more than one hit from a nitro.
• The glop drop AI is disastarous. I find explosive blocks more dangerous to me than glop drops are currently. They mobbed me in their normal form, then morphed into attack form once I had moved away and they were chasing me. Perhaps give them a roll attack, or the option to merge into a giant glop drop or something? Also, make them invulnerable to damage when in their attack form.
• Dust Bunnies are like knocker runts. Their attacks are just as easy to avoid, and they have half the health. Increase their attack speed or decrease their wind up and perhaps give them the ability to teleport like wolvers or something.
• Grave scarabs are mediocre. They should track you once they begin their attack sequence instead of just flying in a straight line. Currently when they spawn in big groups and all get aggro'd to you, you can simply kill the entire spawn with a single swing of a DA.
• The new level design is nice. I like it :)