This is a really easy trick, all you have to do is get the quest, Fate of Karabor, drink the elixir and port into the scenario. Once you are in the scenario, kill all the mobs to either the right of the left of you and slowly start moving towards the stairs on the lower level, killing all mobs that run up. All of these mobs spawn down at the bottom of the stairs, give 500-600 rep each and respawn instantly and 3-5 at a time. I don't think this will make it into live, but it's a nice way to test your characters durability with new changes and also level up.
I did a video guide for anyone who's confused