...Ha Ha...Mandlebrot! Shows up everywhere doesn't it? Couldn't have said it better myself.
When my children ask me questions like "why are we here?" or What is "our purpose"?,I try to explain that exact description of "duality" as the reason we have chosen to come here. If the other side is supposed to be somewhat of a utopia,than all we know at soul level is "good", or the "positive". I believe that is why we come here,how can we appreciate the love if we haven't experienced the hate? How can we appreciate abundance, if we don't know lack? How will we ever learn how to forgive, if never given the chance to be wronged? This is that same balance, as you pointed out. To see the light,there has to be dark - light can't exist w/out it. As in any other case under the sun, where there is positive there is negative - one can't exist w/out the other...and they both exist and thrive here in this melting pot of duality we call earth.
Where else could one learn those cycles or patterns of life and the dualities that create them? To me this life, this planet, this existance that I live "here", is a learning tool, to perfect our soul's perception of consciousness.
I believe we evolve our consciousness by merely being here to take it all in, the duality that is.
Bad, negative, - all good. Just different levels of it like you said!
My opinion... Good witch - on ALL levels !