There is no 'learning curve' here. I loved ninja gaiden because it was challenging and fuggin hard.
PROTOTYPE is hard in the sense that there is so much much going on and your lock-on camera doesn't move means you can never stand still long enough to get your barings, especially with those hunters charging you.
I was in the mission when you first meet the hunters and have to lead them to that military base. I was running around like a freak because I couldn't stop long enough to force the damn camera around fast enough to target them with the rocket launcher, and the claws are little help because while YOU are juggled by their combos, they can lay into your while you're performing yours, and their buddies can just take a swipe at you and your juggled to death, not to mention being slammed by 5 hunters in that tiny place while you're trying to pick up a weapon. That is not challening OR hard, it is pointlessly infuriating because of the terrible camera, which makes the one in ninja gaiden look inspired
so I said "screw it" and uninstalled it.