Yup. Increases MH dmg of course at the same time like how discordance works when you use MA and EAC on special skills. Just on primary skills.
Uses Skilled Mythic, 2 Multi Attack, 2 Extra Attack, as much push the limit possible, some hero points, timewarp and/or cosmic power and you have a very potent Barrage. But that would be the case for any skill in pvp but barrage is good.