Great feedback, and thanks for playing!
Upgradable units are definitely in our roadmap. And I appreciate that many people are not loving how squishy the orcs are, so we may rework our combat a bit as well so they are not quite so impermanent. We do also plan to improve the mana gaining frequency.
The flame trap being single use may have been a bug; they are not intended to be single use. Although if a hero already has a burn status, then adding it again will not stack it (if that's what you meant).
A note on the post-processing; there is an option in the settings menu to turn off the CRT effect. :D
Thanks again for playing!