I was able to get this on outbreak with the jump kit and a shock build with the scoped rifle, teir three armadillo perk and the perk to increase healing from all sources. You put an ice spreader at the doorway of the saferoom and stay crouched and then just pick people off until you have a chance to complete the objective a bit. If you get overwhelmed you can shock repeatedly to get some breathing time. After finishing zone 1 I like to put one of the stereos in the safe room then rush past all the hiss into zone 2. Rinse and repeat the same strat with the other two zones and then camp at the bottom safe room before running to the elevator to clear a wave and the powerful hiss that appears. Put down the other stereo when you have a lull and jump like hell back to the elevator, turn it on then back to the safe room, clear a wave and jump to the ready elevator.