I haven't seen many good games that run on a blockchain, but Steemmonsters is, imo, the best one around, drugwars is cool concept and eosknights too, but eosknights lacks in development, their whole market is screwed, their items kept dropping and there weren't enough players to buy the items from the market, and they haven't created any system to decrease the supply in the market (just like it's happening on Steemmonsters)

Imo, the way to fix the excess of card in Steemmonsters is

1. Do what you said, increase the stats to make the cards that aren't used more widely used, just like League of Legends(LoL) did to a champion called Karma, they did a whole remake of the champion since it was the least used champion. After the remake the champion started being used, even being used in some pre-league tournaments.

2. Create a repair/broke system, for example, you can use a card 100 times before it breaks, once it breaks you can't use it unless you use another card to repair the first, any card can be used in the repair! Making the whole market buy low priced cards to repair the good ones! The card used for repair would go to the nuls account(maybe, haven't figured this one out yet).

3. Create a system like EOSknights has, where we need "water" to evolve the cards, this water can be generated by consuming cards, this would allow a further decrease in the card supply and another use case for the cards... probably moving some cogs around to make the whole Steemmonsters market move...

Maybe I should contact the team in order to see what they think of this system... don't really know who to contact...