(кто-то называл багом что от мобов в инстах убежать нельзя, это не баг)
Monster Chasing

Monsters will only chase you for a specific distance before returning to their patrol area. So if you want to avoid a battle, keep running until they leave you alone. As you run, you can rotate the screen around to see behind you to know when you can stop running. Note, in instances monsters will not stop chasing.

(это про агро, у каждого моба есть список всех кто его бьёт и всех кто лечит тех кто его бьёт, как я понимаю, пока моб жив, все кто попал в этот список останутся в режиме боя)
Monster Hate List/History

Once combat has begun, monsters keep track of damage being done to them and also keep track of the spells being cast. This includes healing spells, or spells that buff other party members. If a monster sees a player doing a lot of damage to it, or casting something it doesn't like, it will then turn and attack that player.

http://www.worldofwarcraft.com/info/basics/combat.html
(в самом низу)
You cannot eat or drink while in combat. You are now considered "in-combat" if any nearby monster is engaged with you.

Сорри, что на английском, ибо взято с офа.