Ever since I started playing, I was questioning why there were two Training Grounds. I understand they are different, but it seems redundant nonetheless.
Instead of two training grounds, I was thought it would be helpful to have a "Card of the Day" event to replace one.
Essentially, this event would feature a common or uncommon card and have objectives related to that card's type, color, skill, etc. This would be a fun way to cause players to rebuild decks, help new players to increase their card list, and remind all players of some of the unique functions and play styles that the diverse card features offer.