So, this glitch/bug has happened for at least a month now. Battanians all of a sudden turn into fur balls in combat, which is completely game breaking cause you can't see any of their moves. Are they planning on fixing this anytime soon?
Just like Cu Chulainn, some Battanian warriors are able to transform into a ferocious monster via 'warp spasm'. What you're seeing is exactly that.
On a serious note, I believe its being caused by both the Noble Bracers and Warlord bracers, items which you see on Battanian lords pretty frequently. Recently, I've seen it on Khuzait Darkhans too, thanks to the warlord bracers they were given..