That might be true. The advantage that The Coin gives you is highly dependent on the deck that you have. In that particular deck that I used in the simulations, the advantage is rather large. For a deck consisting of stronger (higher mana) cards, the advantage is much smaller. I think it's basically due to the fact that a 2-mana drop vs 1-mana drop is much stronger than a 7-mana drop vs a 6-mana drop.