Even with no scaling the mobs would be much easier than they were back then.
Wpvp?
They dont.
I think that’s been a given with WoW though. As soon as we received the Cataclysm update to classes which gave us access to our core class mechanics earlier on and stronger talents we were much stronger in the world.
I still think it would stand with great level disparities though, things like Redridge into Burning Steppes or Swamp of Sorrows etc. The mobs while maybe not as strong in the past would still definitely be threatening.