Before I get into the gunk, I do want to mention you might want to take your Jewelcrafter there, if for nothing but the "rare" quest that drops. It is not a BiS by all means, but it does have some decent stats if you need to fill a slot. It is Bind on Pickup, but free gold and a free (kinda) trinket isn't a bad deal. A few Elementium Bars (5), a few Obsidium Bars (5) and Demonseye (2). Although it's still sitting in my bags, I figured I would hit on it for ya'll. 
Ok, ready for some information? Now depending on how lucky you are, and how much Blizz and the RNG loves you, I have heard you can get 3 EPIX per run of trash, but I received one with two runs (just shy of an hour). What I did was run around the "circle" of ZG (don't forget to reset the instance for 5 man heroic before entering).
If you see the map I posted, follow the outskirts of the circle. The mobs you are looking for are:
*EDIT - April 29th, 8:33pm - As of hotfix posted at Blizz, the gurubashi's no longer drop epic loot, however there is still word that the needlers are producing them.... =)
Like I mentioned above, the mobs are non elite, and they are "yellow" (other than the Venomtip, you can aggro them). The are usually in packs of two or more for the Guru's, and the Needlers are soloists (although they do hang out near each other).
I did this on a i347 rogue, so no biggie for most classes, other than the stealth that I used. The best way that I got to the area is when you first enter the instance, take a sharp left, and follow the "rock ledge". You might aggro the fishies there, but keep going, as they cant follow you (they are fish after all). With a little bit of stealth (or a pot if you dont have the ability) you can get to where the mobs are (starting at about 11 o'clock on the map above).
Now just farm to your heart's content, when you kill the mobs, go back to the front, do a "soft" reset to get the "trash" back, and farm again.
I am not going to cover my GpH, as it will be completely different depending on how many drops you get, and what the going price is on your server, but if you are more of a "solo" player, it is a fun thing to do, and you just might get a few drops. Happy Farming!