We almost get the kill yesterday in 1 hour just killing the green and the red head, but the instance server got disconnected. Within the 5th and the 7th head the healing is a little bit overwhelming but with good raid cds it can be surpassed. Our raid it lvl is like 500 and last tier we get 7/14 hc. So i think its pretty doable the kill without killing the blue one in 10 man normal, at least.
Our raid comp was: tank; drood, dk, heal; priest, pala, resto, dps; warr, rogue, mage frost, drood balance, lock affli.