Pretty fun! Played it the whole way through and it took me just under 4 hours. Pretty solid in terms of content.
The upgrades feel mostly well paced although it does feel very slow at times. Maybe it's because I prioritised economy upgrades, I don't know.
Other times, it does seem like I'm stuck behind a hard requirement to progress, such as a certain skill or character. That can be okay but a couple times I felt forced to go back to farming instead of being able to get resources while trying again.
This is another point, it feels like you can either make progress on beating levels OR gain resources by playing already beaten levels. Again, that can be fine and is bound to happen with incremental games, however, this is almost exclusive here which can get repetitive...
Oh also you may well know already but the knight is uh... completely broken haha. It rendered me full and entirely immune to all damage ^^'
All in all, very solid game! I do like the your incorporation of new mechanics to help with resource gain like the rare elites and the crit drop bonus ; they're indirect increases to income and feel interesting and synergistic! It especially feels good to land a critical on a rare resource ^^
Good luck with the development going forward!