https://us.battle.net/forums/en/wow/topic/20752528876
/console worldPreloadNonCritical 0
Every person that has had loading screen issues since the last patch said this fixed it for them. Blizzard had changed it so everything loads before your character does. Prior to that your character loaded sooner and other things would continue to load after you were in game. Insane that they couldn't figure this out on their own since they had to have known the issue.