The last boss IMO is the easiest one in the instance. The only time he would be hard is if you don't have a bar showing his casting. Otherwise its simply "jump with your shamans when he roars" and "run through to behind him with your tank when he starts a smash".

If you can avoid those 2 abilities nothing else he does hurts at all - I hardly have to heal on him. I've ran this on normal a couple times and heroic 4-5 times and never once has the last boss hit any of my guys with a roar or smash. Also, tank him at the very max range from your DPS - when he turns undead, the closer he is to your undead when he roars the more damage he does. On heroic, if hes at max range, it does like 2k damage to my shamans, hardly worth worrying about at all.