Parmandur
Book-Friend, he/him
How is the term "dark age" offensive? What are you on about?
It originates in a period of propaganda, designed to denigrate one culture (Medieval Europe) in order to fluff up another (the so-called "Enlightenment").
The term is simply not used by historians or social scientists anymore; the "Dark Ages" were a time of political decentralization and a dearth of written culture in some area for a limited time, but saw a general improvement of less sexy tech (mills, bridges, roads agriculture, etc).
Oriental at least has the benefit of referring an area that is the Easter part of a landmass, but similarly involves over-simplifying and denigrating a foreign culture.