This article is missing Cyber domain’s nature by treating is as more of an administrative, organizing concept and artifact:
1- The presumed “arbitrary separation” in Demchak and Dombrowski paper refers to drawing cyber borders (Cyber Westphalia) between states and not a new warfare domain.
2- The fact that Cyber domain is digital and that there are common networking and computing (the 4th C in C4) elements across all domains and Cyber does not make it any less eligible to be a domain than the fact that tanks, airplanes and ships all have wires and use ordnance.
3- The defensive and offensive capabilities and skills of CYBERCOM and warriors are fundamentally different than other domains. To the contrary, spreading it across other domains is what creates stovepipes, duplication, C&C and and integration nightmares. It does not fit anywhere else. May be it will merge with Space/Electronic/Spectrum to a new domain but not yet.