I have a small nitpick about the mark upgrades.
It's good in the world with those badass massive HP hulks, but having 150 HP with the AI3, AI4 and AI5 pretty much makes you untouchable. Ive beaten False Gods with simple rush decks.
I think the Mark Upgrade should only be for the world. That way the other AIs are just like classic elements!
Its always nice to have the option of playing it classic against the AI you like. That's all.
The AI 1, AI 2, AI 3, AI4 and False God buttons will be removed in the final version (And replaced by a random-system which lets you choose an enemy level area, lets say Level 10-20, and you will then battle a random enemy with that strength). You will only be able to find those guys on the map. And False Gods will be more difficult because you have to beat at least 1 of his minions before him, so you probably won't have all health when you start your fight against FGs.
Anyway, there won't be classic farm-battles against thsoe old 13 AI3s, for example. Because the new Level 30-40 random button (which has about the same strength as AI3?) will have at least 50-100 different decks.
And precisely because the mark upgrades make you stronger against the known enemies, there are new enemies with even more power which wait for you to challenge them, so that thing won't get boring.