The most powerfull trigger would be:
When a task is modified!
Afterwards with conditions you would not even need the two triggers for "completed", or "assigned to me".
All attributes of Planner tasks should be available in Flow, of course...
It would also be helpful if there was a trigger that could notify you when your name is mentioned in a task.
It would be also useful to have a trigger when the task is moved from one group to another. For instance, in a Scrum approach, when it moves from ToDo to Backlog or viceversa.
It's interesting if we can be notified when a task is changed of buckets!
I think this is ultimately why we are not embracing planner as a wholesale task management product. If we could update a sharepoint list when an item is modified this would be so useful!
What is needed mostly is the "When Planner Task is modified or updated"
Of course, this would all be for naught if we are unable to update the tasks in SharePoint that was created using a flow triggered by a Planner Task Creation.
In the end what is needed is a way to create a persistant link between tasks in Planner and Tasks in Sharepoint. Shouldn't this be possible using MS Flow?