I have created lists and hashtags as a work around. I also use a #now (this week, this sprint) #next (next week, next sprint), #later. I also have used todo, doing, done as lists and move tasks from one to the other as they move forward (also adding a QA/Review is good) - this way also you can share each list with various people. Try doing this and see how it works.
You can just use hashtags as a workaround (#low #medium #high) and then just filter by that.
This would move wunderlist for me into the category of being able to use for work projects (would be amazing actually because then I could share calendars with teams as well).
Of course the question is what goes in the calendar?