I think communications management plan and team list/responsibilities plan are equally important part of DDP. Communications management plan provides instructions and guidelines on who to contact and the right questions to ask to resolve an issue during the course of a project. Team list/responsibilities plan is equally important as every member in the team is required to be proficient in their own duties apart from backing up a team member in their absence. I think efficient communications plan and versatile team members makes their roles more agile and flexible and therefore contribute to the project wholly rather than strictly defined roles and responsibilities.