Why are we running with Valeera in Delves for Midnight?
If they wanted a rogue companion, Voss is right there. And they can even justify a healing spec with her being ex Scarlet.

So Liadrin abandons Lor'themar and runs to the sunwell to beg the light for aid.
The sunwell presumably summons the army of light/paladins into the room to aid her.
This is backed up due to the well being used as a portal before back in TBC and the fact we know the light can apparently just teleport you around if it really wants to according to the Arathi crash landing in Hallowfall.
But during Legacy of Arathor, they introduced the concept of Scions which are basically light beings that presumably chill on Azeroth and do divine intervention if they feel like it.
Additionally we know the light can creature visages of death characters and pretend to be them, this is the justification for Saurfang and Varian showing up in Sepulcher. The light was cosplaying for Anduin.

So the real question is.
Where the fuck was Thalyssra, port the Horde in. You're Nightborne, you're literally the best telemancers in the setting currently, go save your husband. Especially when the Matriarch of the Blood Knights flees like a coward.
Bet they just didn't wanna make a Nightborne cinematic model

So why do the Horde and Silvermoon have to suffer because Alleria and her Alliance Void Elves are fucktards who doomed Azeroth to being invaded by Xal'atath.
Why can't Xal'atath just go invade Stormwind first instead and kill Turalyon while Alleria's busy in space