https://www.wowhead.com/npc=38485/darnavan#comments:id=971181:reply=148238
alternatively, have a druid root him.
You can also kite him, with a frost mage or a hunter snaring him repeatedly. I haven't really tried any other cc, so you might be able to polymorph, freeze, slow, etc him as well.
I just randomly tried this today and was very suprised it worked. Only drawback was that I was healing and had to drop tree form, and once he bladestorms you can't CC him.
https://www.wowhead.com/npc=38485/darnavan#comments:id=974528
PS: Immune to most CC: shackle, sheeping, repent...
https://www.wowhead.com/quest=24875/deprogramming
You just need to tank him. He's immune to sheep but other CC seems to work. He also puts sunders on the person tanking him.
He was immune to Cyclone's last night, as well.
He is also immune to Fear, Mind Control, Shackle, possibly Death Grip (unconfirmed if our DK missed or if he got Immune) & Slow The only form of CC that worked so far is Entangling Roots
Can confirm the grip doesn't work but it seems snares like chain, roots etc do.
He isn't immune to roots, we had a druid use entangling roots as soon as he spawned and kept him there for the entire fight. He because immune to them if he uses his Bladestorm like ability we found though.
https://www.wowhead.com/quest=24875/deprogramming#comments:id=984467
When he spawned, one of our Death Knights death gripped him to the back of the room
https://www.wowhead.com/quest=24875/deprogramming#comments:id=965061:reply=147163
Me and my raid did this today and he was immune to hunter trap.
Von 
Von