We killed him yesterday for our first raid on him. We killed him on the last try.
As stated above, the damage input is insane in the beginning of the fight and cooldowns are huge help.
We had two prot warriors and a DK.
The DK freed whelps and Storm Rider, whereas one prot warrior freed the Nether Scion, and the other (me) pulled Halfus.
We switched at roughly 4 debuffs stacks, but you must be vigilant because sometimes your stacks get from 2 to 8 in a second.
We killed the whelps firts, then the Nether Scion, then we freed the Time Warden, killed the Storm Rider, and offtanked the time warden until halfus's death.
Vocal communication is essential for a good tank rotation. Bring 3 tanks and the fight will be more easier, provided you bring good healers too.
Nerf Rock, paper is fine