Thanks for the awesome feedback, as always!
> Something horrifically overpowered but I've never managed to get to do is a team consisting of all Scotts, each armed with an axe.
This is a great idea! I think the only situation where this would fail is against a spawner deck (zombie fam or imp/chomp/critter), unless you could really boost their health to outlast it.
> I feel like if the upgrades provided equivalent value to what gems of the same cost as the unit would provide, then it would be more worth it. Because I could buy gems that raise everyone's stats, or I could buff one guy, inconsistently.
This is a good point, it's important to balance the cost of gems vs. upgrades and it may need some tweaking still. Of course since upgrades boost abilities it can be much better still, but as the game stands now I think stats are a bit more powerful than abilities, so it tilts in the favor of gems perhaps. I think the buff-everyone gems may be a bit too cheap, as well (especially compared to the random-two gems).
Relics are going to shift the balance of power a bit, too. They'll have global effects some of which will make certain abilities more powerful.
Please keep the ideas coming! And let me know if you think any specific minions or items are too weak (or strong, but I like a few OP minions, I just don't want any useless ones)!