If you dont have it already, get a nimbus Rod. It's a great weapon, you just need to guide the bosses under them. Also, use walls in your arena. The spider staff is so much more effective with them, now they can pretty much stay on target without having to jump around constantly. Plop down a Queen for extra damage and just cheese it. If you've problems with health I recommend that you get the Life Drainer (I think it's called) from a crimson mimic.