Are you sure that the bears main target is not Rook?
I tank heroics as well on my bear, my co-tank is prot pala. He looses Rook to me (even with his CDs) when I do pot+cds at start. I tank He, but my main target is always, always the one nuked down. Ofc our DPS difference on pull is roughly 100k-200k in mu favor... All I can tell is that even w/o CDs I can peel any boss of my co-tank w/o a taunt if I try...