The criticism was pretty trivial anyways. It's not like the ranking of NPs has ever been terribly consistent (for instance, God Hand, the embodiment of all the labors of Heracles, by far one of the most famous myths in Western culture, has a lower rank than the legend of Lancelot beating some dude with an elm branch). Personally I'd make the rock-armor C-rank, but there's nothing outlandish about making it B.