This is my personal opinion ( its not intend to harm or discriminate individual or beings or entity)

I prefer CARD BANNING/NERF method instead of adjusting rewards. The main issue certain cards has too much advantage in game ( A player will use that advantage to gain more wins and bots will emualte that winning formation as well) As case refence MTG ( magic the gathering) and LOL autobattle chess ( league of legends), both game regularly monitor ranking system by seeing which card/unit/creature/etc are constantly used and getting too many wins at above average or perfect win.

In MTG banning/nerf, since its both physical and digital, they schedule banning every quwater ( unless its emergency banning).

In LOL battle chess banning/nerf, its digital game and they adjust the card stats evry season by nerfing.

FOr splinterland case, we could use Nerf method by not disturbing the original card stats but adding another layer (nerf layer) on top of the original stats... think of it like equipment (shackle) equip on banned/nerf target monster. The task would need to constant review game rank in both format and every season. ( Example of lama + kron combo, since summoner are the heart of the game. the question vomes, to ban/nerf summoner or monster. My suggestion is either ban the summoner or nerf the monster)

As for rewards pools, I like to see grain or other future minerals be replaced which able to change every season 😁