But this is a poetic outpouring of love and supplication, and is always viewed in light of the entire corpus of Orthodox theology, at which Christ is the center, and where Christ is God the Son, and the Theotokos is human.
And as some have pointed out, when we venerate a saint, who is a member of the body of Christ who has achieved theosis and is in Paradise with Christ, we are in a sense venerating Christ himself. For without that union and direct participation in the energies of God, there would be nothing to venerate.
We really don't know if this is a far cry from the level of veneration of the early days of the Church, since all was oral tradition at that point. We must use caution, and not assume that what was believed in a given era was all written down, and that what we have access to today after 2 millenia is everything that *was* written down.
It is important to remember St. John's final words of the Gospel, when he said that if all the things that Christ did were written down, the world could not contain the books. Some of the apostles had died before all of the New Testament was written -- their faith was entirely based on their direct experiences and oral tradition.
St. Paul's statement that "all have sinned" has been interpreted in various ways, most commonly by pointing out that Mary was born with "original sin" -- i.e. she had a tendency to death and corruption, and indeed died.
Much of it is just a mystery, but again, given that statement of St. Paul, one would have to believe that there must have been a clear and universal understanding in the early church that morally guilty actions on the part of the Theotokos were *not* included in what St. Paul was talking about. Otherwise, there would have been controversy when the teaching of the Theotokos living a morally guiltless life began to go from oral tradition to actually being written down.
The important thing about Orthodoxy's approach to the Theotokos is literally right in front of our eyes in our iconography, where the Theotokos is basically never portrayed apart from Christ. Christ is always included in every traditionally painted icon of the Theotokos, even if it is an "unseen" appearance such as the Annunciation, where he is taking flesh within her womb. Even in traditional icons of the Nativity and the Entrace of the Theotokos, there is a small icon of the Annunciation in the background -- connecting her explicitly to Christ.
"O cause of all blessings" is supplication? One wonders indeed at which point does veneration morph into worship! And all along I though God was the cause and source of everything and all, especially all blessings.
I can see why the Protestants cringe, and I must say so do I, at the words of such supplications.