I've been there as well on a light monk built for party utility rather than max dps. It's really just a tipping point thing - once your dps gets to a certain point the fight becomes trivial. If you can't get to that point it's impossible. The right weapon in this case almost always makes enough difference to tip things in your favor. Oh, almost forgot - force damage works on it as well. My weapon I've used for awhile is a force burst of greater chaotic outsider bane and it works like a charm.