Playtestable Wildcards
There should be a system which allows players to playtest decks in Play with wildcards they do not own. You should implement something like a system where players are awarded special "tokens" for wins in premium drafts, or weekly events, and redeeming these tokens allows a player to play something like 3 games in Play where they can play up to 4 or 8 cards which they do not own in their deck. With the current wildcard system, if a player is trying to build an original deck, they have no way of knowing how well a deck might work in the standard metagame with one or two playsets of a couple different rares. They might spend a large number of wildcards on playsets of a couple of rares, and in playing the deck learn that those rares were the wrong cards to add, or that they were unnecessary, or that the deck simply does not work. In the process the player loses numerous wild cards, and is discouraged from further spending wild cards in the future. This leads to players building their own decks less often, and more often trading in wildcards in to build already-proven metagame decks. Metagames become less diverse, and players spend less wild cards as they only play one or two decks. If players can playtest cards they do not own, they can more efficiently use wild cards and build new decks. Demand for wildcard "tokens", awarded with play in something like weekly events or drafts, leads to increased desire to play in such events. Increased efficiency in the use of wild cards also leads to a greater demand for wildcards, as players are more confident using the full extent of their wild card inventories, and such a demand also leads to a greater interest in purchasing packs.