Similar to Professor Putricide's Phase changes you can Invis through the Twilight Councils Phase 2 to Phase 3 transition.
They will (at the correct HP value) capture all your raid members in a gravity shield which prevents you from moving/any actions during the the council physically forming for the last phase. You can time this transitional mini phase with Invis to avoid the Gravity Shield entirely. Which nets you worth while dps time.
*Warning* You may build aggro during this phase. If so, let's hope your tank is very quick with his/her situational awareness.
Alternatively you can cast Flame Orb/Frost Fire Orb prior to the Gravity Shields. However, you need to aim the orb in the direct center of the room. This has to be casted nearly perfectly because the council has a 2 to 2.5 second time prior to them converging in the middle of room where they stand in the corners. Your orb will do damage to the council while they are forming when they finally reach the center of the room where your Orb is waiting for them.
You must remember that the orb will 'die' if it is not contact with a hostile target in about 3 to 5 seconds. While this dps is not game-breaking every little bit helps :P
If this is somewhat difficult to understand I will keep checking this thread to answer any new questions.