John 1:1 "In the beginning was the Word, and the Word was with God and the Word was God."
It may have taken 300 years to form a formal doctrine, but the gospel of John (and other books of the New Testament) have been teaching it all along.
It is interesting to note that the writings we now know as the New Testament weren't formalized as "scripture" until about 300 years after the death of Christ either. Would you also say, then, that since it took 300 years to formalize, the selection of books included is somehow in error?
You're rehashing a bunch of stuff that's already been hashed out. The issue is that of the holy spirit, whether it is part of the Godhead in heaven...scripture says "no" though some think otherwise.