What's Inside Counts

If you don't have a dispel for Guardian Tak'u's heal (Waves of the Hydra), kill the Priest of the Hydra first.

(edit: grammar)

This quest is solo-able. Use whichever interrupt spell you have only when it tells you to or you will die. Bliz has set his major casts for all classes so you are allowed just enough time in between. If you're having a hard time use a flask like that your spec calls for and bring a good potion (healing and maybe one with the 25 second buff like Vermin's Bite).

He is surrounded but four priests. I recommend killing the Priest of the Hydra first and it's a bit of pick-your-poison if you get the chance to attack another. The priests that were not pulled will disappear. After that, he comes to life and you can fight him.

Stay moving and do so especially if you see anything under you other than concrete. The reason why Guardian Tak'u is difficult is because of the fact that you have to constantly and quickly keep moving out of his casting areas.

These are the links to the priests and their corresponding buffs to Tak'u:

Priest of the Hawk buffs Blessing of the Hawk
Priest of the Serpent buffs Blessing of the Serpent
Priest of the Direhorn buffs Blessing of the Direhorn
Priest of the Hydra buffs Blessing of the Hydra

Tak'u, himself casts Gusts of the Hawk, Lightning Strike, Waves of the Hydra, Wrath of the Direhorn.

Good luck and don't give up!

Hunters, I recommend killing the Hydra and Serpent priests first - you can avoid the Direhorn spell easily enough and the Hawk spell didn't seem to hit too hard, but the other two are annoying if you don't have Silencing Shot.