The problem isn't the player count. The problem is the expansion genes which are horribly unbalanced.
You're the first person I've seen say this. The general consensus I've culled from reading reviews seems to be that the expansion genes are really weak and bland compared to the originals.
Not saying I don't believe you, but can you elaborate? I'm still waiting on my copies to arrive, and I opted to purchase both the core game and expansion in one shot - sight unseen.