You can't do it while blocking and you have to press down as well to BS low attacks. (iplaywinner.com)
Hold back on the controller to block an incoming high or mid attack and hold down back to block an incoming low attack. (player.one)
Ailments in the game include stun (skip a turn), charm (may target allies), vulnerable (takes double damage from the next attack), enrage (targets the last person to hurt them & lowers area attack effectiveness), and disarm (lowers attack power for their next move). (zeboyd.com)