About mission of art I could say in a few words that the most important thing in art is : ART MUST ENJOY US , to have the happiness to comtemplate it. The artist's enjoyment of pleasure with which he works is the heart of his art.
Without heart doesn't exist art! The first condition of the artist is to love what he is doing, to be his joy first , and trought that , to offers joy to the other. And the beauty there is in our eyes we can feel what we like or not.  The artist expresses himself and the spectator can make choise of his expression. 

U know, unfortunatelly Farajanov is not very popular even in Georgia :(( only people knows about him. But i'm really proud that this gerat director walked in the same streets where i'm walking now!!! and about art as a a language... from my point of view Art in XXI century has broken the boundaries between Medium, which was hidden from us before, and Mediator-narrator of that "story", way how it is expressed. IT IS NOT A SIGN, IT HAS NOTHING TO SAY ABOUT SOMETHING OTHER THAN ITSELF! therefore u can't measure it and usually comments are inappropriate... all u can do just feel it..

PS How well known is the film director Sergei Parajanov in Georgia? Here in the West very, very few people know about him; even my friend who studies at the Amsterdam Film Academy didn't know who he was until I showed him "Sayat Nova."

Having given it more thought, I have to agree with you: just as man is not a perpetually happy being, so too is his art not always happy or uplifting. I only know a few paintings of Magritte, but they're good examples, of course. Which brings us back to the question =D : what is the mission of art? How about "art serves as the language for all that which can't be expressed through everyday dialogue?" Sograsitev? And what about Dada? Do you consider the works of Marcel Duchamp to be art?