Weapon swap bug

"You cannot use this weapon. It's stats will be ignored"

Is what I'm getting by trying to weapon swap on a druid. Someone mentioned special runes are limited to one, which is the case here... but we only have on active special rune active at any given time with weapon swap, leaving the other weapon inert. This feels like an unintentional bug. And if it's not, it should really be changed.

I want a similar setup, but one fast attack and one slower. But I can't do that now without nerfing my damage.