I think we could improve our positioning during phase 4 of manoroth. Reviewing the logs, it appears that multiple people are getting hit by the cone attack because they are standing next to the OFF-TANK. (This could also be described as the off-tank standing next to multiple hapless victims, but that would be WRONG!!!)
So, the empowered glaive thrust hits the tank and a wide cone, then the massive blast knocks him back (and sends waives of death after him), in a 1.5 second window, the off-tank taunts and takes the second empowered glaive thrust, which also has a wide cone. The off-tank cannot stand in front of the boss or he will take both empowered glaive thrust hits and possibly die. The off-tank also cannot be standing next to hapless innocent victims after he taunts, or they will die. The answer, so far as I can see, is for the raid to all stand on one side or the other of the boss, so the off-tank can stand on the other side.
Then, before the push-back, everyone should move in front of the boss and one of our many druids should hit roar. At the end of the push back, everyone gets a massive speed boost and returns to the starting position NOT in front of the boss.
Well, if all stack on one side and off-tank is on the other side there is no way someone will be hit once current off-tank taunts the boss.
It means that if someone is hit - they are not where they supposed to be.
This can't be solved buy choosing another place where they supposed to be...