This is what I do when I solo, timing it around my Growing Rage skill. (15 second 60% crit buff, 1 min CD)

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1. I group all the mobs up to the first room in the corner by the spawn point, activating Growing Rage early! (cd is 1 minute, you see) I use Graviton Slam/Gravity Well/Singularity to kill them all instantly.

2. I wander down the hall and kill those annoying 4 random guys. I continue.

3. I don't bother with the door: it's 5 guys who'll reset if I'm solo.

4. I run into the large room to trigger the spawns, then go up the hall.

5. I bring the upper hall to the edge next to the opening of the first large room. All 30~ mobs will have spawned by now, and my Growing Rage will have just barely finished its cooldown.

6. 30-MOB-INSTAKILL! (Most of the time. Might have to kill a few stragglers.)