Since my Priestess is not from the alternate reality, she can confer with the Naaru in shattered Outland whenever she desires.Xi'ri is of the Sha'tar, who came to Draenor aboard the Tempest Keep after it was destroyed. The only two Naaru on Draenor at the time of Warlords would be D'ore in Auchindoun and K'ure in Oshu'gun.
She already needs the amulet to be able to go even near Karabor, because the echoes of the dead are haunting her.
Storytelling restriction. If they didn't make him weak somehow, he would be a god and most of the story we experienced would never have come to pass.Seems like a common theme for Velen to be shitty at his job without a Naaru to hold his hand.
Also, he did see Azeroth's future and the cataclysm. he just didn't think it was important enough to do something about it, because he was concerned with the fate of countless worlds.
basically the Padawan looked into the future at the cost of the moment. :<