I do believe that communication is key to the success of any project. However, one thing that I really liked, which you highlighted, was Number 3: Develop clearly defined plans with assigned responsibilities.
I think that goes absolutely hand-in-hand with communication. One of the worst ways that a project can fail is when everything but each individual’s responsibilities are laid out. Therefore, small tasks that should have been done clearly are often left to fall through the cracks because Person A assumed Person B was responsible and vice versa. Therefore, as you stated, having clearly set responsibilities are a definite need for any project to be a success.