My reading of the early history of Jude, 2 Peter, 2 John, 3 John, Revelation and Hebrews shows that they had a very rough ride for the first 400 years (and more) of the Christian Church. (Where was the "FDS" during those heated debates? Were people such as Origen, Irenaeus, Cyril, and Athanasius, etc., etc., members of the FDS??)
There are too many details to go into here, so I recommend the article by Professor F.W. Beale in Volume 1 of "The Interpreter's Dictionary of the Bible", article: "Canon of the NT", especially pages 523-532. If you email me, I can provide a copy of these pages in Word format, which then permits words to be searched.
(The doubt of Paul's authorship of Hebrews is indicated by its location in the NT: whereas Paul's writings are placed in order of their length, Hebrews is not positioned where it otherwise would have been - not that Paul wrote any of the "Pastorals").
Doug