Where is it T.T

I looked it up on Xenon.co.uk as to the location of Punishing Shot. I got it for my PvP character, and now I want it for my PvE character really bad. Trouble is, I don't think that it's where the guy who posted it says it is. Either that, or the boss doesn't always appear.

And, please, before you say "You should look harder", I don't think I could have. I killed everything that moved in Snakedance. And I tried the Search function, too, and came up with squat. Anyone here capped Punishing Shot, or maybe you know a trick that I'm too newbish to know about?

fight your way to the top of snakes dance.
if you dont see the boss on the way to the top, keep zoning back and fourth between snakes dance and dreadnoughs drift till he appears at the spawn location at the top of snakes dance

good trick. guess I'll keep trying that until it works =/

[EDIT] Found it on my second time through the map, on the first attempt of that try. Go me.