well, that was a design decision it seems, to build up atmosphere or w/e, and you can use the torch to kill mobs (although only the warrior can pick it up), and new weapons are scattered everywhere. so you just pick up the torch, go through a tunnel, then swap it for a weapon. like I said, it doesn't seem like loot is important, there's no inventory, armor or enchanted items to pick up
I enjoyed Gears of War, and it had been definitely built with co-op in mind, same here I guess. you can breeze through it on the lowest difficulty to get the hang of things, or try to beat it alone as a challenge.
Resident Evil 5 is another good example. I beat it in co-op with my friend. but to tell you the truth he can be worse than an AI companion at times, still I don't think it would be as fun. so you might have a point there