For those of you who are not prepared to die, I cannot stress how important it is to play in co-op.
Co-op will not save your ass most the time, but it gives you the ability to distract any enemies and hide in the corner to cry. Dying all the time doesn't make this game difficult, it's the fear of death. I walk at a turtle's pace trying to spot hiding enemies and traps, then a phantom invades my world and stabs me in the arse. I have a zero success rate so far at killing invaders. They're the ones who really make this game unpredictable and enjoyable (That may not be the word you use for it).