I've seen a couple people say that Ysera's rebirth in Ardenweald invalidates her death in Legion. It does not. She's still dead, she can't come back to Azeroth. But her existence hasn't been terminated altogether. It's bittersweet; a victory that doesn't erase the past loss.
If anything it's a continuation of seeing what happened to her after she died. If Ysera being in Ardenweald invalidates her death. Then that applies to everyone in the Shadowlands then.
