See, I don't agree, I think there's plenty of possibility of variety. Though I do get your point.
I still think Argus could have done for a full expansion pretty easily.
There has to come a point where we simply can't adventure anywhere else on Azeroth, though. They can only hide so many landmasses before it gets absurd (and it has long passed absurd).
And I don't get that issue you use, either. Distinct looking zones somehow become tiring? As opposed to several zones all looking alike? I feel I'm missing something here, so my apologies.