I have the following gameplay suggestions, which I think might serve to make the game more interesting.
1) Field 2 Promo creatures only. This way, the composition of the deck would be more important than the overwhelming amount of promos. And you have to seriously pick between promos.
2) Every 7 creature deck can designate 1 other-element creature. Increasing possible combinations of abilities.
2) Every hero gets 1 equipment slot, which doesn’t take a creature’s place. This will likely vastly increase the unpredictability of battles.
3) Special heroes can field 2 slots, or a terrain. To be honest, I’m all for every deck to get a terrain and an equipment slot, but maybe that’s too random.