I'm confused by your post. Are you saying that Christ sanctified us once for all on the cross based upon Hebrews? Are you saying that Paul made it up and that the gospels are the only rule? Not sure what you are saying. Would you clarify?
+Paul's ministry is decidely distinct from other Apostles (for obvious reasons). The Gospels simply tell us what the Apostles remember Christ doing and saying. +Paul actually interprets what Christ did and said.
+Paul is the one who gets into the nitty-gritty stuff, such as chastity, celibacy, women not being allowed to speak in church, dispensing with the Law, no need for sacrifices (Heb 10 again), and so on.
This stuff is night and day different from the Gospels. But, +Paul was commissioned and sent to sell the dying Church in Israel to the Gentiles. He knew that the Gentiles will not accept Judaic dietary practices and circumcision, and he urged the Apostles in Jerusalem to change or perish.
Let's face it: if I have to make a distinction between the Church and Protestants, I would say the Church is mostly based on Gospels; the Protestants mostly on Paul. Take out the Gospels and the Church is dead. Take out +Paul and Protestanstism vanishes!
The Gospels are about Christ. The Epistles are what +Paul makes of Christ. Now, having said that, he may have well been inspired and his words are those of God. That's the position the Church has held (although Hebrews were probably not written by +Paul), and still holds.
+Paul saved the Church from certain extinction in Israel and in that he is next to +Peter as far as the Church is concerned. Other than that, I will be honest, I have problems with many things +Paul says, but as always I defer to the Church and trust that, although not obvious or often talked about, the Church sees no problems with Heb 10 and similar chapters.