Things you will need for this exploit:
-Need to be an alliance toon (sorry horde)
-Must not have completed the quest "It goes to 11..."
*for those of you that are unsure if you've completed this quest, this is the one where you gain control of a harpoon gun and shoot buildings to alert guard and then you shoot them out of the sky. If you've completed the quest then sadly you will not be able to do this exploit.
-Finally you will need a person to group with that can potentially stay in howling fjord anywhere in the zone (preferably the valgarde inn)
-This isn't required, but highly recommended. 10% xp shoulders as you will be getting xp solely from killing mobs, and as much rested xp as possible.
If you were to do this quest out of a party you would find yourself shooting the buildings one at a time and then killing the guards that are alerted for a measly 58xp a piece. For some reason when you're in a group with someone and they're still in the zone you will see a jump in xp gained per kill to over 1900xp. We thought this was impossible, but try it out and see for yourself. You can also shoot more than one building at a time if you spam the button, and more buildings mean more guards. You'll get an average of 4 guards per building and so long as you're using the harpoon to destroy the buildings whenever it's up you'll constantly have guards to kill. Doing this method I was able to level my mage from 70 to 73 in about 5 hours. So if you've got some alts sitting at 70 that you just haven't been in the mood to level, try this out.
Just a heads up. The harpoon has a health bar and if you get overwhelmed by guards they can easily destroy your harpoon and it takes several seconds to spawn a new one. Also while the harpoon is destroyed the guards will change their focus to you so plan your farming accordingly. The use on the harpoon only lasts for 5 minutes at a time, so even if your harpoon isn't destroyed you'll be kicked off after 5 minutes and the harpoon health will hold over to the next time you use it.
Have fun with this exploit and happy farming
by GMUNYIFan