Some scattered thoughts:
Last time I made it to the ossified overlord with I think a mystic or a sunmender, I had a single target heal build so the chaos spell ended the run.
This time I went with the basic lesser+greater heal guy, picked up circle of healing, instant heal and finished the dungeon first try.
The rest of my team were melee guys so they all fit within the circle with the precision upgrade and it was a cakewalk.
The dodge time on the arcane magistrate's abilities is really generous. It might be a good idea to err on the side of caution and then add an optional modifier to make enemies faster or tougher, it could work like the shrine in bastion.
I got baited into buying shield bash before I realized that none of my guys had the shield skill despite using the sword and shield model.
The library could use a section on the various available characters.
Being able to globally upgrade the stats of your character is lame, I get that metaprogression can be fun but when presented with a flat stat boost players might feel like they're trivializing the game by getting those upgrades or that they're supposed to grind for them if they're struggling.
There's no reason to show outdated upgrades in the healer's spellbook, also upgrades should probably be sorted by spell rather than written down in the order you get the upgrades.
The DPS prioritize button worked great for Cromwell.
I stacked crit chance and got the extra crit upgrades for instant heal and it was hard to tell when spells critted in the chaos, I'm pretty sure that there's a sound clue but maybe the numbers could be of a different color as well, maybe a lighter green or gold? There's a lot of numbers flying around so just making them slightly bigger is not very clear.