Okay i am not going to give you 20k gold /hour guide because i am an atheist, i don't believe in wonders.
Also: this IS common sense, and probably posted few times before, but still i am going to do it as it worked great for myself 6):!
What..
I was watching the prices of [Eternal Life] over the last few months and on my realm EU Aerie Peak, the price per one is 27g atm. :confused:
Where..
Wintergasp Steppe of Life. Left down corner on the picture below.
Risks...
WG is a pvpflagged zone so you could face some opposite fraction trouble.
Also there might be people on your realm farming it too. When i farmed there was only 1 hunter there who was also farming. Perhaps without him i would have a better profit. twocents
Result..
After 35 minutes of farming i got 10 [Eternal Life]. The mobs usually drop 1-3 crystalized life's. They respawn pretty fast.
After putting them on AH they sold almost immediately got me 250g.
TIP..
Try to farm during raidhours or early hours to avoid other farmers or pvp activity.
Cheers & Goodluck !