I'm not saying subjectively right or wrong that The Royal Managerie (end of SB story mode trial) should be nerfed, but objectively it screams nerf. SE can't have an instance at that difficulty as a part of story mode because it's going to gate people from content (same logic behind Steps of Faith). They will lose subs otherwise and it's bad for business.
The same defensive rationales will be made, i.e. "all you need is a premade," but once it's at that point it's objectively too much for story mode. SE knows, or should know, they absolutely cannot afford to have story mode be at a high enough difficulty that it gates people from content (it's required to unlock the Verity vendor)... they should, and already are largely, saving it for the optional stuff, i.e. EX primals and savage.