You know you getting bonus experience if you kill group of mobs whatever they are marked heroic or not, so if they to hard for you dont have to give up just kill one then escape, come back and kill another mob of same group. Even if it was group of 5 mobs and you escaped (yell for help and run away) before killing last mob, you can come back and kill him and you get same bonus experience for defeating encounter as if you killed full group at once.
Not sure if this work, but if you trying to advance alt this way, you can load your main kill all mobs in group except 1 then relog alt and kill that last mob for bonus xp.
 |
