I was able to 5box VD doing the "Kill BLM" Method mentioned above. It has a lot more risk involved, but it's w/o a doubt faster once your group perfects it.
Setup: RUN BRD COR GEO WHM Ygnas. Literally any DD or support could replace Ygnas for a 6th so feel free to experiment with everything.
Buffs:
•BRD: March x2, Mad x2, Ballad for WHM/GEO. Elegy/Nocturne stuff.
•COR: CC SAM and Chaos.
•WHM: Barstonra/Barpetra and standard WHM buffs.
•GEO: BoG/EA Fury. Indi-Frailty. Entrust Barrier or Wilt. Save Demat for final zerg.
•RUN: Save Valiance, One for All, Battuta for final zerg.
Mechanics:
Phase 1:
•Just kill the 1st 2 adds asap. Focus PLD 1st to force invincible then swap to the WAR.
•Once adds are dead you're free to force 1st Bene.
Phase2:
•After first Bene, it will spawn BLM.
•Silence BLM.
•Move everyone away from NM except RUN.
•RUN solo kills BLM to force Sorrow of Gu'Dha on only the RUN. It will only use this once.
Phase 3:
•Killing BLM starts phase 3.
•Quickly move WHM back in to cursna/heal RUN asap. NM will go after a DD.
•Now it will only use Torment of Gu'Dha and nothing else.
•Each time it uses Torment of Gu'Dha its shield will drop.
•Demat/Valiance/One for All all help to reduce Torment's damage.
•Torment does not have a massive range, so WHM can easily stona/curaga4 without having to worry.
As mentioned, I'd say the "Kill BLM" method is very dangerous, but a lot quicker once perfected, but the "Keep BLM alive" method is overall safer while taking a bit longer due to changing Magic/Ranged/Phys weakness phase.