WoWDB

How this quest is completed is not as difficult as people think, because the way it is done is extremely convoluted and unintuitive and most people seem to not know how it works, which makes it take ridiculously long.  You do not want to just go into this zone and grind mobs -- it will take you forever.

You will notice when you enter the zone that you have two fill in bars.  One is "Forces Twarted" and one is a morale/happiness bar for slaves that you have freed.  The "Forces Twarted" is the bar that you need to fill to complete this objective, but the other bar is what enables you to complete this quickly.

As you are entering the zone, look around for Outcast Darkscryers which are Arakoa mobs surrounded by a swirling purple bubble.  There are two of them in Skettis -- one on the far east in some trees on the border to Shadowmoon Valley and another in the far west.  Remember where they are.  You will need them later.

So step one is free some slaves.  Skyreach Labormasters drop  Talon Key.  Other Skyreach mobs can drop them too but not at as high of a percent.  Target these guys first and collect keys, and free slaves.  They will follow you around for a short period of time.  While the freed slaves are following you, they gain happiness for the Skyreach mobs that you kill.  Remember two things: Happiness will decay, and the followers won't follow you forever so keep an eye on their duration.

When you have a decent amount of happiness or your birds are about to "expire," run to that Outcast Darkscryer you noted earlier and talk to him.  When you select his chat option, the happiness bar will transfer at a 1:1 ratio to your "Forces Twarted" bar.  Have 20% happiness when you talk to the guy?  Now you have 20% more progress towards quest completion. 

This is the way to fill up that bar quickly.  It will require you to kill far less mobs than just endlessly grinding, which is what most people seem to be doing.

Assault on Skettis https://www.youtube.com/watch?v=6hotLKp0Rbk