In the dmm version kamihime there are event quests and one of them require you to beat ultimate with R only team (I am not sure when they were added, but they should be coming soon to nutaku). So in other words current "endgame" = dmm version. And there is quest that require you to beat ultimate with Rare kamihimes. I am pretty sure that "perfect team made only of SSR" isn't needed for that.
But Ragnarok? Ragnarok difficulty will pose problems mainly because there will be no trash mobs that will help in filling burst gauge and boss will have almost always only 1 charge orb.(or maybe always?) Ah, and you can attempt it only once a day.
Still, I don't think you will need "perfect SSR team" for this. Well, that's about advent battles. Now if you want to solo ragnarok raid... Then you will probably need something ridiculus to be able to pull it off. But why would you do it is beyong me.