Big thanks to the OP. I am a step-by-step person so I am posting the order for clarification (nothing against the OP who we owe a lot of thanks to!).

1. Gather, enter
2. Kill room
3. Two portals will appear
4. Split into two groups, one going in each portal
5. Kill room, saving Antlion Drones for last
6. Kill last Antlion Drone at the same time (each group needs to kill within 3 seconds of one another)
7. Take center portal
8. You will now be rejoined
9. Kill room saving Antlion SENTRY mobs for last
10. Kill at same time
11. Take center portal
12. You will be in a hallway now, feel free to open chest then proceed south
13. You will all enter a room with mobs, kill room, leaving Antlion SENTRY mobs for last
14. Kill Sentry mobs at same time
15. Take portal up top
16. Claim AF and weep tears of joy!