Mythic: Council of Dreams

Doing this at max level, its all about managing the %.
They have their own health pools.
You only get a 10s ish grace window once one dies or it resses with full health.
Got it about 5 tries in, by being very careful about % especially from 10% down taking them down evenly.
Not sure about dps, but being a level 90, 277 ilvl tank meant that dmg meant nothing.

Just focus on the % going down even, especially if you have no burst.