Justin,
St. Gregory was talking about the extremes of two heresies which said completley opposite things. Are you calling the GOC of Greece a heresy?
You seem to be turning the question of new-calendar Grace into as big of an issue as their heresies are. The Church is primarily pastoral, it is not a political party. You are not on a "middle road", you are simply closer to the fire, accepting the Grace of heretics which you know is a lie. Sure, believing in the Grace of heretics and those who accept their teachings by communing with them may make YOU feel good inside, but how pastoral is that when you deny people coming over a true Baptism? How pastoral is it when you teach Christs flock, that while there are differences, there is really no difference in the end and everyone is "the Church", and thereby lead people into the "impious and profane" desolation of heretics?
"Extreme ecclesiology" to the world are those who don't agree with them the most. "Extreme ecclesiology" to the Church is that which approaches something which is not accepted by the Church. Who has "extreme ecclesiology" when accepting the Grace of heretics?
The difference between the GOC and the ROCOR is a question of pastoral care and responsibility.