I can only assume the mobs have been set too high deliberately and will be nerfed when we're live, or it's an oversight. I don't expect to one shot them but I have 167k pot with the fervor buff, and I'm geared out with all the adorns and 5 or 6 heroic items I've picked up. I've never done beta before, so don't know if the mobs fluctuating from easy to impossible to easy to impossible etc is normal, but as things stand right now, people aren't getting past this zone.