Thanks a lot! You definitely read the Fighter correctly. He really is carrying most of the party right now, and that's something I'd like to rebalance in a future version (maybe by adding a fourth hero).
I see the Archer a bit differently though. His main value is being able to target enemies further back in the formation, and while he's not as strong as the Fighter, he's actually pretty close. Still, if he feels noticeably weaker overall, that's definitely worth checking.
And yeah, Quick March is probably the odd one out. It improves gold-per-minute by making runs faster, but unlike most other upgrades it doesn't really change what happens during combat. That's something I'd probably rethink too.
Thanks for the detailed feedback!