I beat this game a week ago in single player and it have lots of flaws. Maybe the multiplayer is better? It seem your AI partners is incredibly dumb. They barely attack at all when it comes to enemies. I always out attack them 5:1. Not to mention, AI have a hard time following you when it comes to none flat surfaces. They either stand still or drop to their doom in constant bases. Most of time you have to keep taping the shoulder buttons to warp close to you. And when it comes to those puzzles that you have to light up two different orb at same time, your AI partner can't even help your there. You have to do all the dirty work. The only use for those useless AI are meat shields.
Anyway, this game is really easy. Just buy lots of potion and increase potion capacity. It seem like all the bosses have same strategy, you can either hurt and heal with potions or circle around them and attack them from behind, AI are way too stupid to even counter it. It took me 10 hours to beat this game.