Your reason for using concussive only armor is partially correct, it does die last but using it does not make you survive longer. People started building only concussive armor to be selfish and put the armor losses on their allies when they lost nothing or they lost much less. Now any player that knows the proper ratios builds only concussive armor so it is the same as if everyone had all type of armor.
it's not being selfish, it's being fair, the armor loss will be distributed fairly amongst the members who participated in the battle (unless some has less than needed). But I agree, using all concussive armor will contribute nothing towards the battle result. So if u don't mind being the one who lose more armor, feel free to use beam and explosive armor