And I mean to say : Shadow priests use the shadow/void for decades now ... (could someone define when first shadow priests came to be in lore ?).
Furthermore since the beginning of this expansion priests grow tentacles and they got the option to surrender to madness .
Anyways I am not really hyped by Alleria using the void since me priest does it for a dozen years now and I don't understand the whole lightforged crew jumping up and down about it (oke i know X'era is about as simpleminded as Odyn - not as valorous though- but anyways there is some weird feeling since every player knows they can use the void freely and we stand in owe with Alleria doing so and even the jedi master LS giving major lectures about h2 use it...).
TLDR It's not like inventing the wheel half a dozen expansions later.