It's funny, when I played through Dawntrail I actually felt like the way the split zones were handled were a shakeup from the normal formula-both zone return visits happen soon after the first visit, compared to previous expansions where at least one of the split zones isn't completed until much later in the story after other zones have been finished.

I do agree though that a stronger change in formula would be appreciated. My main concern is the "change" would just be less zones overall.