As a hunter, you can set your pet to tank the boss, and the boss wont apply the debuff to it(the debuff which heals the boss for 250k per hit).
This way, you can do the boss, solomode.
Only tested @ 25 man Heroic.
Notice: Once the boss has applied the first Mark, it'll stack its energy and get stuck on 100%(if there is only 1 player).
Enjoy.