The only purpose that the higher level equipment would serve is like you said, continued play of the hard raid along with PVP activities that had level advantages enabled like Iron Banner and Trials of Osiris. Other then that there is no real reason go for those things unless you just want them to say you have them. That's why things like the elemental primaries were good and served as good rewards from activities like Raids and Trials of Osiris cause they were that icing on the cake that typically made the effort worthwhile.