I can't see any RP argument for a berserker not wearing a mage poncho. I don't care how easy it was to get. That's their thing. They are not only trophies but in a way I think they are also meant to be frightening to their enemy. You have this scary barbarian mage hunter who is wearing the skin of other dead wizards. Yeah, that might be scary if you're a wizard.

It's like the movie predator. Predator hunted warriors of other alien species and took their skulls for trophies. Did he give a fuck how easy it was to kill and rip out green beret dudes skull and spine? No way.

I can see an argument for non-mages though.