Currently on Runetotem EU, Artrius the Heartless is bugged with a constant immune. As he's immune, he still gives weapon skill: So...
*Although this is only on one realm and will probably be fixed ~quite soon~ (Which by Gm's standards, is about 1 day) you may want to keep a look out on your realm. I've seen this happen twice on mine. If someone can find out how it's done: Wicked*