Raid Difficulty: Normal
Summary of Events:
Sundering Doom and Doomed Sundering deal way to much damage to the opposite realm(the realm that sees the purple swirly thing). You can take a look at the video below provided as evidence(at 31:31). Here it seems that no matter how far you are from the boss when he casts it, it will still hit you a bunch. I'm not sure bout the calculations.
What should happen on Retail:
As shown in the video from Fatboss (at 9:29, you can see the players in the spirit realm are just as far as the swirly thing is taking the area), you do not need to go way to much back from the boss when the purple swirly thing is being cast, and the damage is not so big.
Evidence:
Below a video from today's run, 3-4 runs, you can take a look at all of them, or the time which was specified in the above section.