I too spent a few hours at this camp with very little luck getting tainted to spawn and then when it did spawn and I killed it, no corrupted. Now I was insta-nuking all the goblins in and around the tower, including the tainted. Reasoning that in the "olden days" most players had to pull the tainted to the wall and then beat it down over some time, I decided to do exactly that with my next tainted pop. I pulled him to a corner and then instead of insta-nuking I used my melee "skills", such as they are, and even at level 100 a druid's melee damage isn't enough to put down a tainted goblin in one swing. He dropped to 15% and then started running. You have to be careful here since I lost sight of him when he ran and by the time I put up track he had snuck to the top of the tunnel and was almost lost in the wall. At this point since I couldn't melee anymore, I nuked him and sure enough a corrupted spawn upon his death. I actually had to target the corrupted using /tar because he was mostly in the wall. THIS one I wasted with one nuke and then was able to loot my epic piece using /tar and /loot.
So while it's probably just "rumor and innuendo" I suggest pulling the tainted outside of the tower, slay it slowly and then be sure it doesn't run away from you!