this can be done with higher level pets as well and all servers arent fixed yet but if you use higher level pets then your has to be within 5 levels of the pet killed like if you are fighting level 15 critter then you should be level 15-20 or lower than 15, the lower you are the better if you can win because it gives you a difficulty bonus
US servers just went down. I believe this is over. edit: Confirmed. Just got on my 83 priest and went from 60k xp battles to 3.5k xp. =(
On US I think they just did another hotfix. Logged to swap toons and all the servers were red. Exited game and it did a small dl