This guy is pretty tough for a ret team in heroic mode, I have to kite him in circles the entire fight to avoid the freeze... and I had to setup a macro to rotate hands of freedom on the DK tank so that i would always have one available when he does the power overwhelming buff. Whenever he gets the buff I would stop my team and kite him through the frost puddles on the tank, the puddle both snares and damages you so make sure you don't drag your rets through them with you

I just tried to bruteforce him down the first few times without any movement and got fairly close a few times but died during the freeze breath thing. I think if you were geared and speced for PVE it could work though. My team only has PVP gear with a few random PVE pieces on the tank, tank also has nothing remotly close to a tank spec so he dies pretty easily