I did this quest later on, because I didn't know about it earlier, and had already done Arachnophobia. There are a lot of venomspitters all around Stonetalon Mountains. They are near the road, on Webspinner Path (this is the road you are on when you go to Sunrock Retreat for the first time -- it continues north and eventually leads to the Alliance town and Desolace over by a Mirkfalon Lake), from about Malaka'jin all the way to the path through the mountains that leads to the Charred Vale. They are also around the Venture Company site, before you get all the way into it.

Creepers, on the other hand, are almost only found in Sishir Canyon. So, yes, you do want to do this quest with Arachnophobia, just so you don't have to go back to Sishir Canyon just for the creepers.

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well it took me forever and i had to ask for help like three times but i got it to turn in the quest go to 72,95