Do you really think that God cares in which direction we pray? I think it's more important that we wait on God by keeping His commandments rather than looking towards the East. Symbolically, I think it's great that we look towards the east in our Divine Liturgy but do you really think it's heresy if we don't?
It is not a heresy if you do not pray in the direction of the East. God will listen to our prayers anywhere we are and in whatever direction we pray. The point is: are we, in our prayers, awaiting the coming of the Lord? Are we hoping to be joined to Him soon? If you are standing waiting for a friend you are supposed to meet, won't you be looking in the direction he is going to be coming from? The Lord is our friend whom we are longing to meet and are therefore praying looking in the direction from where He is going to come in His glory (Matthew 24:27).