That might be possible for older players that chooses to stay in the Bronze league but for newly joined players that don't want to spend more than the initial $10 for the Spellbook, the nerf makes it very difficult for them to rent cards till they get to the Silver league. Unless of course, they get really lucky and win their ranked battles constantly, or get some good cards that they could sell in the market.
I'm not saying that's impossible just really difficult. And although I understand the devs reasonings behind the nerf I still think that the amount of Credit one could get from loot chests are a joke. They could at least make the minimum 10 Credits or something.