We do damage from the spawn. As soon as the boss "tags" you, we split up into a triangular formation:
Continuous
Angular ______________________________ Parallel
When you get "tagged" again, switch to where ever you need to go. This formation ensures no one is tethered and that you always have Phase Synergy for the damage buff.
Whisper is clearly the weapon of choice here. Well of Radiance is a must. Hunters should use Golden Gun. Titans are worthless.
You should be 631 by the time you get to the boss. 626 absolutely minimum, but that's pushing it.