Rewards are already behind enough paywalls. Spellbook, Power, Focus Points cut for card level to league cap. If they lock up reward cards its just like adding worthless potions to rewards. Its no longer play to earn, its pay to play and pay to unlock rewards.

they seem really quick to make changes to making playing and earning more difficult while taking forever to deliver on prodcuts already sold via kick starters and other sales. I thought vouchers were going to be a one time use thing anyways, Why are we desperate to keep around a 3rd currency. SPS, DEC, Vouchers. If they want more uses for vouchers build it into lands, crafting, etc.