I hope they fix this soon, same bug for enemies caught in Zephyr's Tornadoes and Vauban's Vortex. Not only Xaku's ghost guns don't attack them, but you also can't cast Gaze on them.
Now I always dread going in with pubs with Hydroid/Khora/Zephyr/Vauban as Xaku, knowing I will become useless. :D