Love your thorough feedback and appreciate your thoughts!
Good to hear you had no performance/stability issues, that was still my main goal.
About the other issues: Its somewhat nice that most of that was already on my radar. The fireball thing is one of the weirder things that happened to me too. I have no clue whats happening there (as well as with the 1 room dungeons) and that will be one of the main things for next DD i guess.
The dungeons are indeed smaller as i downscaled them from 100x100 to 75x75 in order to see how that feels. Got the feedback last time that levels are really big. Since content wasnt a priority, these numbers will change just as much as projectile speed etc. So let me say for all your (appreciated and noted) comments about content: that will all come in time. ;)
Missing walls are a thing im still thinking about how to do it in an elegant way. Right now i only render walls that would NOT block the view. So single wall tiles in the middle of a room will just be that black, empty tile. Walls will need a closer look anyways, because they need a) variations like ground tiles and b) corners/pillars should look different than "regular" walls.
Showcase friendly arrangements are a good point though and will go on my todo list. Will do my best to bring as many improvements as possible to next DD.
Thanks for the input again and keep working on ToK, its inspiring to see progress on a similar project.