willyk, rent rate is not proxy for desirability because most businesses and citizens are not in the market for new office space. You're only discussing desirability to a relatively small subsegment of firms and folks, who ARE, by virtue of membership in such a subsegment, very image-sensitive. They're buying that public posture at the same time as buying convenient access to HSR or DNT or whatever else. They are usually waiting for someplace to be "trending" before they want to be seen onboard.
I don't think it's justified to act like things with differing levels of desirability have to be considered separate communities for anybody outside of CRE. Inside CRE their goals are different than our civic goals. It seems obvious to me that people can want to be part of someplace that has multiple tiers and entry points - a real downtown neighborhood is a large umbrella, not a version of the exurbs where every price level is named and sold separately -- the Lakes of Woodall Rodgers segregated from the upper echelon in the Pointe at Woodall Rodgers and the senior living communities in Sunrise Heights on Woodall Rodgers. Applying exurban logic to the central Dallas neighborhoods demonstrates, to me, the brittleness of the exurbs' small-umbrella approach.