Is this the return of powerleveling? What good/bad can come from this?
*** Encounter Locking ***
Encounter locking restrictions have been relaxed for non-raid encounters. Non-raid encounters have been changed as follows:
* There are no longer lock icons on you or your enemies.
* The first group or person to attack a creature will receive any reward it grants upon death, including loot and experience.
* Other players can assist in your fight by damaging your enemies or healing you.
* You will receive a reduced XP reward if your group contributes less than 50% of the damage needed to kill something.
* You can change group options and add/remove people from groups while fighting (note that fighting raid encounters still prevents this).
* Damage credit is correctly tracked if you add people helping you to the group before something dies.
* Any faction increase or decrease the creature grants will be applied to everyone the creature hates when it dies.
* In an upcoming update: If a group prefers to play by the old rules, they may make their targetted encounter exclusively locked (thus preventing help unless asked for).
Here is a detailed article explaining these changes.