Play enough and you'll start to get segments collectively good enough to get around 6:30 with the rare warlock boss in the final room. Under 6:20 though is beyond me. Even 2 rare warlocks in the final room might not get me under 6:15. Being limited by the DPS of your max fire rate with the rocket launcher vs. the collective HP of all the enemies required to be killed becomes the real enemy. There are maybe 20 seconds to be save if you could somehow move at light speed, but almost the whole instance is just limited by how many average shots it takes to kill enemies.