In this particular case, I have to say I agree as well. Easy and normal seem just fine for the gate, the way it's set up, and I even dare to say these particular two difficulty levels seem to be extremely carefully balanced. But as for the higher ones, I think I'm not even going to try them unless the way they work is changed in the future. Normal is entertaining and challenging to the point where I still like it and it seems fair to me, but having tried nightmare in the first level and not being able to complete it, my mind is made up. :-)
Lukas