I do know that the health of mobs seems to increase proportionately to the amount of players on, and I suspect other stats may as well. I also think that playing solo has other disadvantages (for example, my buddy was able to kite a 2-star troll to allow me time to reach my corpse just last night, and then were were both able to switch off on aggro whenever the other was low on stamina).

The game is geared towards multi-player, but I don't think it's impossible. Just very hard.

You'll get the usual cast in here telling you, "herpa derpa, no, it's so easy, you're just too dumb, git gud, you're in the minority," but taking on the wilds of Valheim is always better with friends. Maybe you should check out the "Looking For Group" sub-forum here and get a band of Viking brothers to help you out. If nothing else, at least you can have fun and make friends.