At the appropriate level, talk to Coleman Farthing.
Coleman Farthing - NPC - World of Warcraft
If you do his quest chains, he'll give the the quest "speak with sevren"
Speak with Sevren - Quest - World of Warcraft
Follow that quest chain until you get "A daughter's Embrace"
A Daughter's Embrace - Quest - World of Warcraft
This quest will give you a guardian named "Lilian Voss" which has the ability to one shot all scarlet mobs related to her quest.
The mobs are level 11 and spawn quickly so pretty much no down time. You need to make sure you tag each mob as you walk up and down the pathway otherwise, you get no exp. At level 10, they give about 100 exp each.
Took me around half an hour to get from 10-14. Mind you I had the 20% exp boost due to heirlooms but still pretty good nonetheless. By 14 the mobs only gave 60 exp which is why I stopped.
This map shows the location of the quest where you pick up Lilian and the location of the mobs.
http://img213.imageshack.us/i/mobsd.png/
Here are some screenshots
http://img821.imageshack.us/i/lilianexp.jpg/
http://img821.imageshack.us/i/lilianexp.jpg/
Tips: Stay close to Lilian. If you can, pull mobs from a distance. The mobs hit hard, can snare, and interrupt. Also, do not enter the tower until you want to finish the quest. If you accidentally do enter, you can abandon the quest and start over.
Enjoy!