The point remains that the scripture does not contain a claim of self-sufficiency, but contains indications of other revelations given the apostles. Whether they were necessary or auxiliary for our salvation, we don't know because they were not recorded as gospel. Possibly, they were recorded as non-canonical teaching of the Church fathers.
If the scripture were sufficient for salvation, how did the Christendom survive for decades without the bulk of it, and for centuries thereafter without a definitive canon? What does it do to the Protestants who threw away canonical books because they did not like them?
Yes, there are passages in the scripture that state that the scripture is inspired (all of it, including the parts Luther threw out), necessary for complete clerical education, useful to the point of being the absolute proof for argumentation, and not to be contradicted. This is precisely what the Church teaches about it.
Luther didn't throw any canonical books out. The Roman Catholic church added them to the Canon at Trent. "As the Church reads the books of Judith and Tobit and Maccabees but does not receive them among the canonical Scriptures, so also it reads Wisdom and Ecclesiasticus for the edification of the people, not for the authoritative confirmation of doctrine."
Jerome
Jerome's preface to the books of Solomon