There is a vast difference between the OT prophets who condemned the actions of the people (the Church) but DID NOT START THEIR OWN GROUP OF WORSHIPPERS, and Luther and Calvin, who invented their own way of worshipping God. God NEVER erased His People and began a new one. The prophets were "whistle-blowers", but they always remained within the Church.
Your comparision fails.
Regards
"The Church" in the OT became corrupt over and over again, too many times to count. God led prophets to reform the Church, and for God's reasons the Church was reformed, even though it would not last for very long in many cases. Therefore, there was no need to start a breakaway group of followers. God never led them to do that. However, 500 years ago, God did lead several men to break away. Although not to the same degree, He also led either you or the Orthodox to break away 500 years before that. God had His reasons for doing it, so it was done. And if you want to say that I am comparing Calvin and Luther to the prophets or the Apostles, then just remember that all of your Fathers already have that status as a group because Tradition is equal with scripture. If numbers matter so much to be correct, then my side also has a group.