Double Swing - Glitch or not?

Hi there,

As we were cutting a deal with my friend @IllTheMessiah he showed me his new barb gear and then he left town and started using double swing with beast BA and grief BA. The result was that: when he started the attack animation he disappeared from the screen. Then i went hostile to check if this stuff still occurs - same result. Im posting a SS because i don't have a screen recording SW, but its obvious - his name is on the map but charracter isnt there on screen:

http://i.imgur.com/5enx7EB.jpg

The shot is taken during the initiation of the attack. I did a quick search on that but found nothing. Anyone here aware on that matter?