All world bosses are now Tap to Faction. This new system offers every eligible player of the same faction that engages a boss the chance to earn loot. Under the new system, players will only be able to earn loot from each world boss once per week, but bonus rolls apply. Bosses will now respawn more frequently as well.
I guess it's a good idea as people from the same faction will help out the group that's fighting the world boss. Might encourage a little more world pvp even on normal servers since once someone tapped the boss, he has an incentive to go after opposite faction guys who are flagged and try to wipe the group killing the world boss.