As you said he was playing with Venruki and Kollektiv. The best mage and the best shaman in the world.
A gimped spec works when being carried by the best players in the world.
Mage shaman can work with any third class. Warlock could work in that comp if it brought nothing but instant fear while mage kills things.
other then ''One amazing guy'' with ''amazing people'' can do it as I've stated
Different definitions of viable.
Can an incredibly skilled player with incredibly skilled teammates play it and accomplish great things? Sure, but top raiding guilds can clear the hardest heroic content in the game wearing blues - I doubt the majority of the playerbase would consider blues "viable" for heroic raiding.
As for chaos wave, I wish there was some compensation for the nerf in pve - I used to find it handy for feng heroic since I'm forced to go demo to help deal with adds most the time.
Currently a 14/14 Holy Paladin and 10/14 Discipline Priest in Siege of Orgrimmar
Formerly voidspark - 8/8 Demonology Warlock and Restoration Druid in Dragon Soul