Try to complete a daily quest when you have gold cards and you reach the diamond league. Impossible! You can complete a daily quest when you play in your own league in 10 minutes, when you reach a higher league where you don't have the cards for that league suddenly the daily quest becomes an hour long grind(if you're lucky). So, you don't have the cards to play in diamond league and yet the game is forcing you to do it. Let me ask you is that fun? Hell no it is not!
Create an option for players to choose if they want to move up to higher league. When you want to move up there should be an option in the game for you to chose if you want to move up or stay in your league, if you don't want to move up let the system cap your progression. Simple, elegant, will make players a lot less frustrated, and in the end those 2 extra daily reward cards are not even worth the trouble. Your move devs.