Most reformed will tell you that the Catholic Church is "semi-pelagian" because you as well as the Orthodox side of the Church believe that we cooperate with God's will.
Orange II received Papal endorsement but that in and of itself did not make it a dogma in the Undivided Church (it required an Ecumenical Council).
The Church to this day teaches two different aspects of the original sin, and origin of the souls. Just because the east never agreed with St. Augustine does not make him a "heretic."
Obviously the Church can live with both as neither affect the Trinitarian, Christiological or Mariological dogmas of the Church.
That's something we'll have to figure out in that big reunion council we keep talking about. ;-)