Ensidia has a record on this sort of thing. They've exploited kills before. They've bragged about buying gold. They show an all-around "we're too smart for silly things like rules" attitude.
A three day ban and stripping them of the achievement is hardly a suitable punishment. Maybe they're set back a week. I suspect more, since exploiters tend to be compensating for a lack of skill. I'm not saying they're bad, but based on the pattern of exploits, they are clearly not top-quality material. They're not a top guild. Not even close. They're posers who do nothing but hurt the image of the truly skilled. If they had any decency, they'd send apologies to all the true top guilds. But if they had any decency, they'd be 100 spots further down where they belong.
People like this deserve cruel and unusual punishment. A mere bureaucratic throwing of the book is not enough. You see, people like them are a blight upon the world and should be treated with the total lack of human decency which they have earned. I propose a new, inhumane punishment reserved for only the most notorious of exploiters and general destroyers of game and world society.
Create a filter which will take all messages in trade containing the word "anal" and redirect them to all chat and combat logs of Ensidia members who were involved in the exploitative activities.
This will both clean up trade and punish these monsters.
 A late addition, to more fully explain my position.