After logging over 24 hours of the Beta, Hard mode is what I've played through, the entire game regardless of level. I find it perfectly challenging, coming from a lover of Skyrim on Legendary difficulty it's the absolutely perfect blend of difficulty... alone. With multiple people, it becomes significantly easier, I think enemies need to scale to make them more difficult with more people, either increasing enemy level or enemy amount. The most important note of this is the boss fights, in single player I can barely beat the bosses, and upon death I am punished by having to restart and perfect my strategy. Love it! With friends? Stay alive, kamikaze for damage if needed, I need one player to stay alive at all times in order to win. I can die hundreds of time with no resolve, have a friend run out of the room and win. I feel that a solution to this is rather simple, enable your teammates to revive you, but they have a time limit and amount per instance. So as an example.. I have thirty seconds after being downed for my allies to push back the enemy and revive me, bam two revives on me left. Or.. my Allies could have troubles with these enemies and after the thirty seconds I die, permanently until the instance is over, or we all die. I personally say this from completing the entire thing solo, and with friends, all on hard difficulty.