The Scale of Sands
The Scale of Sands is the reputation for the Mount Hyjal raid instance, located in the Caverns of Time. Players will recieve Scale of Sands reputation from both killing bosses and killing mobs all the way up to Exalted Faction. Players will recieve on average 7800 per full clear. This means it will require 5-6 runs in order to reach exalted. With a quick bit of math, about a month and a half if you're running it every week.
Here are the reputation values for each of the mobs inside Mount Hyjal:
Archimonde - 1500 rep