Tamara's taser shouldn't have had any effect on August, since wood doesn't conduct electricity. However, the show's creators confirmed that, unbeknownst to Tamara, the taser is magic.
Snow White/Mary Margaret is shooting arrows rapidly in succession. As she pulls the arrows from her quiver with her right hand and knocks it on the string, pulling back with fingers her right hand, the shaft of the (obiously CGI) arrow is on the left side of the bow, seeming to have passed through it.