I read the following this morning by the Orthodox theologian John Meyendorff on Luther's catholicity:
“Luther’s main intention was to go back to the New Testament, to revive the sense of the God of the Bible, the living God, the Creator and the Soveriegn. He recovers the primitive concept of salvation as a drama, a battle between God and the evil powers of sin and death which have usurped God’s sovereignty over the world... Lutheran theology was indeed a re-establishment of the basic Biblical and Patristic elements in this drama. His concern for the catholic tradition of the church was obvious, and the Augsburg Confession itself claims to be nothing else than a reestablishment of the ancient apostolic faith liberated from all human philosophical systems.”
Catholicity and the Church by John Meyendorff, pp68-69
SVS Press, NY [italics mine].