I heard someone say this was the longest wait for the tainted/corrupted spawns for the druid epic. When i first read about my epic and trying to get these guys to spawn I happened to be in Everfrost farming spidlerlings for silk. I decided to head out and give it a try. I killed two or three mammoth calfs and litterally two minutes later there were two tainted up. I killed them both, two corrupted spawned. Killed and looted the chunk of tundra from one and sent a /ooc for the other. I figured that if all of them were this easy I would have my epic by the end of the week. Turns out I got what was coming to me, camping the tainted aquagoblins for five hours, and the brownies for two more.
I know this isn't very helpful but i thought i would share my experience and lend support the crazy randomness these spawns seem to have

Santug's Gift