As an elder I followed the Society's general guidance but at the same time as an elder you had some leeway to check to see if they wanted to return.
After I stepped down, I made it a point to always speak to disfellowshipped ones, even to the point of taking them out for a few beers. It amazing what you find out.
Disfellowshipping and the subsequent shunning is a way of getting rid of people and then making sure they never get to tell their side of the story.