There are no bosses that unlock via a PvP zone like in Wrath and Cataclysm, instead there are two world bosses that will drop tier pieces and pvp gear when killed. They are Sha of Anger and Galleon. You should do these bosses at least once a week as the first kill will give you a chance at loot, you can repeat this for more chances at loot if you have Elder Charm of Good Fortune to burn. Sha of Anger is guaranteed to drop Claw of Anger on your first kill, looting it gives you a quest to pick up some 476 level boots. He also has a chance to drop Reins of the Heavenly Cloud Serpent. He usually respawns every two hours or so in Kun-Lai Summit in various locations
Galleon is located in the Valley of Four Winds and at 70, 63, near the South East border. He has a chance to drop Son of Galleon's Saddle, his spawn timer is longer than the Sha's.
Below is a quick guide to the bosses:
Sha of Anger
He'll select random people to mind control until they're at 50% health.
He summons adds.
Don't stand in black clouds.
Hits everyone with shadowbolts periodically.
Run back if you die and keep fighting.
Don't stand where Canonballs are about to land.
Stomp is unavoidable, just deal with it.