Planner has great potential, unfortunately, it is quite useless for many reasons. 1. You cannot create templates and then re-use them. 2. Tasks should be able to be locked so they can't be easily deleted by others. 3. If a template was enabled, you should be able to create a new plan based on the template, and when adding or deleting tasks in the new plan, it should not affect the underlying templated. Unfortunately, changing something in the "copied" template, changes things in the template, and vice-a-versa. NOT VERY HELPFUL.
You need to be able to create a template for Planner is the shared Portal space, and when creating a new plan in individual teams sites, it should be able to reference the shared template, and base the new plan on the shared templates. I have tried using Planner multiple times, but every time I get about 10 tasks in, and I start testing, and I realize the limitations, and then I abandon using it.