It took a few wipes the first night to get it all down, but we one shot them now as well. I've tanked this on my warlock for all of our attempts. Ranged tanking is definitely nothing new in WoW or even this expansion. This fight is really easy as a ranged tank. You pick up orbs using rank 1 Curse of Agony, and I can stay in range of my healer as I do it. It seems like that wouldn't be impossible but might be more difficult for a melee tank that has to run all over the fairly large room to pick them up. At the same time, I can keep aggro from across the room if necessary when he becomes empowered and all the DPS switch to him...you never know where you'll be when that happens as you move around the room avoiding bombs and picking blueberries.

Warlocks in particular have a lot of abilities/talents to mediate the damage like Nether Prot, Voidwalker Sacrafice, shadow ward, soul link, and Master Demonologist.

There are very good reasons in the mechanics to use a ranged tank in this fight. It is a pretty different sort of fight though for the player and took a little practice.