They've had to revamp the tournaments. Thankfully, they’re just about all free now so they're basically taking the approach of "we'll pay you to play our game" the sad part is that still isn't enough to attract players.

As you mentioned you have to invest a decent amount to have a chance at winning those tournaments. You could rent but you would probably have to plunk a good amount and if you’re not in the top couple of tiers you’re losing out. But hopefully you can make some of that back in a brawl (if you’re in a guild) or winning more games with those better rented cards. However managing all of that becomes a lot of “work” which can be tedious and isn’t fun to a lot of people.

They need to get more players in. Instead of worrying about burning cards or trying to manage the currently over saturated market as there will be an increased level of demand.