Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood.
Note 7 at Ac 20:28: The word that was translated "overseers" here is the Greek word "EPISKOPOS." This word was translated "bishop(s)" in Php 1:1, 1Ti 3:2, Tit 1:7, and 1Pe 2:25. This lends further clarification to the job of bishops. They oversee the work of the local church.
Note 8 at Ac 20:28: Paul went on to warn these leaders that spiritual hard times were coming to the believers at Ephesus through false doctrines that would be taught. Although the Lord administered rebukes to the leaders of the seven Asian churches because they did not deal with those who were corrupting their people (Ephesus was one of them, Re 2-3), Paul just admonished these leaders to be faithful to feed the flock that the Holy Ghost had set them over.
Just as in Jesus' teaching on the parable of the tares and the wheat (see note 1 at Mt 13:37), trying to discern false teachers is hard and dangerous. It is much easier to discern false teachings. Our first line of defense against wrong teaching is right teaching, and that is what Paul majored on here. There is a place for those in leadership to administer rebukes, but we would have much less need to do so if we were faithful to teach the Word.