Ah you’re right. Maybe it’s been taken for granted that the king of the human kingdom is to be the high king of the alliance.
I think it can be changed. Why not. It’s just a mutual agreement among race leaders. If they think Anduin’s not good enough for leading the entire faction, (and Anduin knows about this, you can read it from Found Memento questline), the high king can be changed. Anduin’s my favorite, but I like all the other alliance race leaders too. I play Worgen and Nelf too, so especially Genn and Tyrande.
I just want Blizz to develop Anduin’s character well. They missed the chance when Anduin couldn’t persuade Tyrande about Darkshore and when Sylvanas fled, twice, so he needs another chance. Like…
This is a good development, I mean, it’s necessary. Since he’s a strong priest.
This is very bad and exactly what I’m worried about. Apparently people can see the same thing. It’s just another Mary Sue. I hate what they did to Sylvanas, and they do the same thing to Anduin? 
And I hope Blizz stop messing with our paladins anymore. They let a Mary Sue EZ defeat Bolvar, they let Guldan kill Tirion with bare hands, they let Yrel go fanatic, and now they try to ruin the character of Uther.
Gees. Pls leave Turalyon alone. If Blizz really really need an Alliance hero villain? My pick is Calia or Alleria. Turalyon could die stopping her, then Arator will follow his father’s legacy as a paladin.