Stinglasher is kind of difficult to find. As far as I can tell, his spawn is totally random where the bugs can spawn, just keep grinding and you'll find him eventually. The only thing I can say is that in all the times i've killed him, he's never been in the tunnels. He's been at the entrances, but never inside(where the minimap changes to the indoor view).

The rogue vale screechers are what you need, they are found south of dire maul and north of the ogre camp in the south. Use the stick in your inventory on a corpse.

The ogres you need are easily found around this area.

There's a lot of Gordunni Mage-Lords around this area. Makes it easy to finish Dark Ceremony quickly.

Run back to Camp Mojache and turn everything in, get all follow ups. Fly to Orgrimmar. Pay close attention and do the following: Turn in "Zukk'Ash report" at 56,46. Turn in "Donation of Silk" and "Donation of Mageweave" at 63,51. Accept "Ripple Recovery" 59,36, turn it in right next to him, back and forth it. Turn in "Parts of the Swarm" & "A Grim discovery" at 75,34. Accept "Betrayed" from him. Turn in "A Strange Request" in the cleft of shadow at 49,50, accept "Report to Witch Doctor Uzer'i" turn in "report to Zor", accept/complete "Service to the Horde" 38,38 Turn in "The Gordunni Orb" at 39.86. Turn in "Donation of Silk" and "Donation of Mageweave" at 37,87. Then hearth back to Feralas.

After you do all that, start circuit3.