If I understand the terms correctly, the Orthodox - Catholic Divide is a “schism” as it is the result of the church splitting over an issue on a macrocosmic level. One bishop went one way, one bishop went another. Who was faithful to the correct, underlying “truth” is determined by which side of the schism you’re on.
This differs from the Protestant “heresy” as there was no common root, per se. The reformation was the result of a completely new “innovation” on how to approach the Christian faith and is not built (perhaps with some pride) on the “fallen” Church it sprang from. Protestantism, is then, a “reboot” of the faith.
Protestants today are certainly not to be regarded as heretics in the same sense Luther, Calvin, Knox or Zwingli are. However, it can be safely said that they are the sons and daughters of spiritual rebellion. The Orthodox, from the Catholic perspective, are sons and daughters of a church separated by Greek-Latin jealousy and pride.
As I have a soft-spot for the Orthodox, I will offer that there have been many Catholics in authority who have given the Greeks some valid fuel for their fires.