Same thing happened to me, except I had two of the spiders dead at the time, and ended up facing two vampires, two werewolves, two zombies, and two spirits. I got turned into a zombie. = P That battle I was not surprised to lose. But I've lost the next four tries as well (two more of which I've lost because I got turned into a zombie). I'm not sure what I'm doing wrong, but I give up for tonight.
I ended up being able to beat it after about a dozen tries or so, the strategy I used was to just barricade yourself in the left corner and torch them as they run up, and 4-way bite to finish them off. You have to get lucky off of the rad bites though.
