This is my first post here so you may have to excuse my explanation.
This is pretty much just a certain place to kill mobs, but I go to Darkwhisper Gorge at the very southern tip of Winterspring on my LVL 60 warlock. You should probably be lvl 60 if you are going here. Simply start to farm the Hederine Slayers. To do this simply place as many DoT's on the mob and fear. Make sure that you keep the dots on as much as you can. Do everything you can to keep them from hitting you. A regular hit will cause about 600-700 damage, and if they hit you with a mortal strike expect at least 1000dmg to you. They attack fairly quickly also. Anyways, these mobs each drop about 20-30silver each, they drop a small amount of runecloth, and also have a chance to drop felcloth. One of the main reasons that I farm these mobs is because they have a .8% chance to drop the Eye of Shadow which will sell in the auction house from anywhere between 150-300g depending on your server's economy. While farming these I have received numerous BoE blues including an Assassination Blade. There is also a Vendor right inside of this that sells 2 felcloth for 80s each, and sells 5 gromsblood for 10s each.
That pretty much sums up my short money making guide for now. If you have any questions please leave a post and I'll try to answer them asap.
Ps. Just for the record, the video on allakhazam of the warlock killing a slayer is very poorly done, Curse of Doom is not very efficient and very slow to kill these. I will work on making a video and will post it as soon as its finished.
I just recommend Immolate>start running away> Curse of Agony> Siphon Life (if you have it)> Corruption> stop and turn around> fear, From there all you really have to do is just maintain your DoTs and keep fearing him. You will have some times where your fear will resist. If you get in this situation, depending on how much HP you have, try fearing 1 more time, if resist again then death coil, if he resists your deathcoil (which they have resisted all of these before) then banish and run away and bandage because at this time your health will probably be very low.
I also recommend being affliction spec'd all the way down to dark pact, and just have your imp out as a mana source.