It's ok for mines to be hard, however, the player has to clear one or more of these areas before they can even begin to upgrade from plains gear to mistlands gear.

But if you can clear the infested mine, then what do you need new gear for? (Maybe the Queen, but until there's something after her, there's not much incentive to worry about it.)

In other words, I agree that mistlands progression is messed up. There needs to be some kind of upgrade prior to facing the hardest content in the biome.