So your team doesn't own Wintersgrasp and you need eternal earths to make some gold or craft an item... well no worries! I know just the place!
The square area of Zim'Rhuk you'll see in the video is surround by 76-77 elite Guardians of Zim'Rhuk, which happen to have a similiar drop rate to the revenants in wintersgrasp.
They drop as many as 3-4 crystallized earths each.You simply run around the square (does that make sense?) following its edges and looking for the mobnames.
I was getting as many as 12 crystallized earths per two minutes and I'm prot. I can't imagine how fast a real dps could do this. Simply kill one mob, mount up, then fly to the next. An added bonus is that they should be respawning by the time you kill them all.