So, I'm not quite sure, but I think that the mission is always has the same stars, like, 'Purchase an item from the stash' is always 2 stars, so, I think it would be nice to add a section in the mission article to include the amount of stars given for each mission.
If the star numbers change, then I'm, sure they are relative to the amount of work they include, ie, a 'Travel 4,000 total' is 1 star, and a 'Travel 7,000 total' is 2 stars. (I checked the mission star count for accuracy)
Just an idea.