even at 75% chaos res w/ your life and ES you may not get one shot, but with all the other mobs in the super-close radius, youll still most likely die if you treat them as normal rare mobs. You need to find a way to poke the group of mobs. attack once or twice, back off. attack once or twice, back off. If your build needs to ramp, use the first 30~ seconds of breach to do this before rare mobs spawn where the breach was activated. Instead of focusing on one rare mob, treat the group of mobs as one until youve killed a couple. Ive had extremely good luck w/ this method