Races will definitely be coming back, and hopefully, they will be a lot more impactful than +/- an attribute here or there. The more they impact gameplay to be unique and different, the better.
I agree that fire mage needs a little something, in particular, the fire orb is too weak. It went from being wayyy too tanky to having no hp. I don't think the orb being a tank really fits fire mage, perhaps an interesting tweak (on top of giving it a little more hp), would be having it leave a flaming cloud when it dies. This will give the fire mage a lot of tactical options. That may be too strong though, burst of flame is incredibly powerful.
Confusion got over-nerfed in the duration, there has been a lot of discussion about how to balance that spell. If the duration is too high, it stunlocks enemies. If it's too low, it feels useless. Dominate/freeze I personally feel are still, absolutely, 100% game breakingly OP.
About the level-up cooldown spells: I highly recommend investing in some of them, they are worth it! Throughout the game, they function as a reusable, consumable level effect. That's the key part of those abilities, they save the non-reusable resources for later in the game. The abilities are also amazing late game, in particular, in the Yendor fight. Each of the three rooms has an energy well, that means at a minimum you get to use them once per room. Combine that with a few energy or power pots, giving you even more casts, and they are super valuable.
The changes to protection did impact rogue and ranger a lot. It is now important to strategize around enemies having protection, and I think that's great. Use elemental damage, or get crits to burst through. A crossbow is very valuable, or it is worth keeping a staff around to swap in if required. I do think there should be a few changes - turrets shouldn't have as high protection as they do, they were already nasty enough - and a few more options to give melee/ranged elemental damage (such as through an elemental buff to weapons talent or the like) would be nice.
If you could select a melee weapon or staff at the beginning of the run, imo that would reduce the variability. Every melee class should take the spear, no question. For mages, ice staff. The starting weapons are part of the class identity to me, and while there should be plenty of gear choices for the player to make, having it so early I disagree with.
I agree that UD gets repetitive, all zones do really. With more development time, I think the idea in Justin's development plan is to add more terrain generators, more vaults, and more enemy types. Each zone will have multiple different sub-zone types. Adding early versions of enemies is something that should be done a lot more, to introduce the player to various mechanics.
There are a lot of opinions about the hp shrooms and backtracking, some players like it, others hate it. I like the lack of natural hp regen, but would probably dislike backtracking if I had to do it much. Well, it's a work in progress, none of these mechanics are set yet.
If enemies specifically aimed to use shrooms, it would change a lot. Not only would a lot of shrooms get used by enemies, but the player would have to destroy shrooms just to prevent the enemy from using them. Purple shrooms do buff the enemies, it gives them their CDs back immediately. Not always that impactful, but multiple summons, or a 2nd healing totem, some enemies it really makes a difference.
A more intelligent AI would be amazing, but also so much work to design and implement. We can dream though haha.
Its great to hear from other players who love the game, I highly recommend you come join the discord :D