With regards to new Cards, in my perspective, production of new card sets are important and should be on a regular basis (quarterly or semi-annual). It is the only way to make the game fresh. I.E. Hearthstone releases new sets every quarter. In our case, it took us almost 1 year before we got Riftwatchers. The game gets stale if an entire year of no new sets.
Supply can never be perfect but I'd prefer we over supply than undersupply. Anything that can't be sold in a certain period of time are automatically burned.
I am on the fence regarding soulbound reward cards. We are built as a tradeable card game which is the opposite of having soulbound cards. I don't see this solving the issue of cards being farmed. People find ways. Besides the farming and selling keeps the prices competitive.