To write a letter of disassociation is to imply the Watchtower has authority over you.
Strongly disagree, at least for myself. Our DA letter was a public (we sent to a lot of people) declaration of independence, that we no longer accepted the Governing Body as having any authority over us. It might even have counted as a declaration of war. We wanted to make sure that everyone knew that we left because the religion was WRONG. We specifically stated that if they impugned our character we would take legal action.
It wasn't long after we sent it that we saw a car group working field service on Saturday morning cross the street to avoid walking in front of our house. Maybe they thought we would sneeze apostate germs on them.
I would say (strongly) that the important thing is getting out of the Watchtower, not the route you took. Everybody has to find their own path.