I agree with bookie on this. I do see a couple issues however.
1. From a programming standpoint getting this game to work with 8 players would require a massive rework of the system just for 1 game type. A temporary solution to this would be to create a hardcore(pro) mode where it's the exact same as the current hardcore mode except the rules of pro mode. So it's bookies idea, only with the normal 2 people, then as the game progresses a 4 and 8 person version can be released. This makes it so that the massive system rework isn't being done for just 1 mode (it's now 2-3 modes, which is no different than what is currently in the game).
2. I'm honestly just playing devils advocate on this one, but as putting a limit on deck CAP for each round would (in theory) help free players I feel it would just put a band-aid on the problem. All the pay players would just have a deck of lvl 50 grey cards, which would once again give them a rather large advantage (lvl 50 hero is cheap). Solution: Not only limit the deck CAP but also limit the card lvl. This doesn't mean they can't use a lvl50 card, it means that it would be lvl20 in that round.