Enemy spikes are ok since they either have boss lv health or have teammates. Your own spikes though tend to run out before they do anything near as effective as just attacking them even once. Would be nice to be able to run them in the deck outside super late game when you already have everything else needed to stay alive. I don't think they need more spikes though maybe multipurpose them, like something where it also gives you a little bit of block to supplement your strats instead of being the leftover card you use when there's nothing else.
Heals...are rather weak tbh. Unless you're stacking them at every opportunity you just never have enough to keep up since there'll be times you just have to soak up 20+ dmg a turn. That kind of damage would need 3-5 cards to heal back, but that'd ruin deck rng early-mid game.
An antidote would be...ok-ish, but way too situational since only a low percentage of enemies use it, I'd recommend a remedy card or something like that which cleans up debuffs instead. It'd be useful against most enemies since they tend to spam weak, vulnerable, and fragile. There's also the new dragons that use burn. It's better to not pigeon hole cards so that more players can experiment with them in the deck.
A counter move for the beast deck is almost necessary if you go beyond lv 1 difficulty. I find that the enemies just put out way too much damage beyond lv 2 so you're forced to play too defensively, but I really like the beast auras early game.
Event wise I'd say to hardcode a non-repeat, I just had 2 runs in a row where all the events were the mirror. It was nice to find out those auras stack...though also unfortunately in one I then went through a gauntlet of full teams so they all got buffed, haha!
If you're open to suggestions on events you could have an investment aura, where it takes a portion of your reward each time but then gives it back 2x after beating the stage. Another is a vampire event where you feed them hp, and the more you give the stronger a card(s) you get back. There's also the idea of bartering with goblins where you hand over 2 cards or 75 gold and get a random card.
As a side note, it'd be great to have an 'exit to main menu' button somewhere instead of exiting the game outright. I lost quite a bit of progress and still can't quite get it back because that's what I thought the exit button would do.
I'm sooo looking forward to cursed gamemodes! I think the best one would be one for starting with a reduced deck: half the attacks and blocks, no buffs, etc. You start on hardmode but don't have to waste money on culling your deck for a while!
OOH a cursed deck! Where each card comes with a debuff, like attacks give you fragile and blocks weak, but then! You have a card that does something equal to your total debuffs! Cursed decks would be an amazing mechanic of it's own!