Funny that missions and evangelism is never mentioned as part of being the true church from most reformed writers.
They always mention discipline, however, such that many reformed churches nowadays rush to discipline but do not similarly rush to train and send missionaries with the same zeal.
As it happens, I think that you are correct to note that the simplistic manner in which the three marks are sometimes discussed can be misleading. The Westminster Confession lists the profession of true religion as the defining mark of the church, as in that is what is necessary to the being of the church. The administration of the sacraments and the exercise of church discipline are better seen as marks pertaining to the well-being of the church.
This understanding of the marks is the only one that corresponds with scripture, because, otherwise, it is hard to make sense of Paul (to cite but one biblical example) regarding the Galatians and Corinthians as true churches notwithstanding major corruptions and irregularities in doctrine and discipline.
I know of people who have taken the three marks to such an extreme that they believed that any irregularity or deficiency in relation to the three marks rendered a congregation or denomination a false church. This sort of purity spiralling quickly gets ugly.
Evangelism is implied in the first mark. You can hardly have the pure preaching of the word of God without it.
You are always complaining about churches covering up certain scandals. Now you are complaining that they are too zealous to administer discipline. You cannot have your cake and eat it at the same time. Mission and evangelism are important, but it is not the church's only duty. If it were, then why did Paul tell the Corinthians to expel the incestuous man when they could have just concentrated on missions instead?
The true church hath her marks whereby she is known: The Gospel truly preached, The sacraments sincerely ministered, discipline duly executed.
For instance, in my jungle area, at what point do the little congregations of villagers throughout my region get to be considered a church instead of a preaching post? If I am trying to plant churches throughout my jungle region, how do I know when I have accomplished that? It is not entirely clear to me.
Pergy, In a Congregational setting, where a group is autonomous and associations are not encouraged, isn't that up to the people involved to decide?