Well, the characters in any horror survival can either be super OP or stupid... xD Its hard to find the balance.
I'll keep shooting out random ideas then. Will try to keep em simple.
We could also go REC style. Several doctors were invited to mansion, after a while they find out that the mansion is surrounded by the army and they kill anyone who passes the outer walls. No one knows anything, no one can do anything. (Or the same thing but with a group of thiefs)
I quite like this one: After months of traveling, a merchant caravan is running out of supplies and its members are starving. One quiet evening they finally reach their destination. But the town is silent, no one is around. All food seems to have dissapeared too. And then, after the sun dissapears behind the horizon...