Not writing about Mr. Locke, but I thought that the statement you made about what preachers need to focus on needed a response.
My response is that this is not what preachers need to focus on; their focus needs to be on feeding their flock, that is their marching orders.
John 21:15-17 (KJV) So when they had dined, Jesus saith to Simon Peter, Simon, son of Jonas, lovest thou me more than these? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my lambs. He saith to him again the second time, Simon, son of Jonas, lovest thou me? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my sheep. He saith unto him the third time, Simon, son of Jonas, lovest thou me? Peter was grieved because he said unto him the third time, Lovest thou me? And he said unto him, Lord, thou knowest all things; thou knowest that I love thee. Jesus saith unto him, Feed my sheep.
This does not preclude preachers from winning souls for Christ, it is just not to be their main focus.