Originally Posted by
Shirai
Eh, not too peeved about that. Relic weapons already have that as "Hidden effect" without having to keep an Aftermath up and unless SE's changed it in this update the damage multiplier can only proc on normal strikes and not on Weapon skills.
It'll likely proc considerably more often than the hidden effect on relic weapons, but even then it's still only an occasional effect.
That said, Mythic Aftermath is already incredibly powerful on its own, and it also lasts considerably longer than that of its Relic and Empyrian counterparts. (Not sure about Aeonic, not much info about that one available yet.)