While it's easier with other people in most contexts, the game can be played solo. Like Dark Souls it's hard because you get thrown against stuff you can't evenly match until you've progressed quite a ways. The highest (current) stuff is still a threat even when you have the best gear. Early stuff is not even able to scratch you, it seems.

It's a game about survival and challenge as you earn your way to Valhalla. It's supposed to be hard to shape you into a warrior worthy to sit beside Odin. Think of it as training.