Todd,
Thank you for very eloquent post. I agree with many things you wrote and yet, you are quite mistaken in this particular case.
Tarkovsky never pursued a goal of criticizing Soviet system. For some reason most people think that Russian (Soviet) artists and writers could create something decent only by rebelling against commies. AS if there is nothing else beyond this pitiful subject.
Maybe it's because those authors and artists who outcried are better known to the West. But their credits were rather low among thinking audience then and (after collapse of comm.regime) are nullified completely.
I don't know why this strange idea is so popular in USA, but, in reality, for the most part Russian intelligentsia have more interesting and important things to explore and tell.
The very point of blaming and reproving social nonsense and regimes is a way too shallow for the most of serious artists. They usually don't go that low, or, at least, do not limit their work to this. It was nothing but a commonplace stuff, simple and tedious, but intrinsic for almost any work of every schmuck of that time.
It's appealing only for mediocre pen-pushers like Solzhenitsin.
Tarkovsky is much much more sophisticated than that.
I saw all his movies and not once. I saw them dubbed properly where dialogues are rendered accurately (not like in those crappy releases with pathetic subtitles that you can rent in Blockbuster and other places). I am sure you know that subtitles in foreign releases are lousy and hardly close to real contents...
Naturally I read all scripts as well.
I studied his works thoroughly when I was working on my PhD thesis. (Not even mention that I knew the man personally...)
Believe me, Todd, all this fuss about depicting socialism and revealing scary truth about Soviet regime was the LAST thing he ever cared.
Even though he had afwul difficulties in getting his movies produced and he suffered from bureaucrats and heavy censorship, he did not really aim at pouring the dirt on socialist stuff.
Tarkovsky was a man of rare spiritual frame, highest human values and aesthetics, lofty morals. Religious in certain way. Fighting or exposing shortcomings of Soviet system was too small and absolutely unintersting thing for him. His aspirations were of different nature, more subtle and ascending to higher plane of human spirit.
In a way (if there is any reference: allegories, parallels, parable-like stuff and other circumbendibus) it was a by-product, which censorship saw and tried to ban, and some benevolent European film critics blew this fact out of reasonable proportions.
Comm.censorship of that time could shelve anything with even remotest suspicion of anti-communist thing in art work, even when the whole work was about something else and author did not even think to criticize anything. Well, life had tendencies to go into extremes.
Quite different thing is books of Strugatski brothers (their book 'Roadside picnic' & script was used for 'Stalker'

. They criticized Soviet realities quite a lot, but even in their books it wasn't most important layer of meaning.
In production of 'Stalker' Tarkovsky forced them to rewrite script 4 times and he threw away all the stuff that might refer to Soviet system, because he did not want to play with that crap. He had other things in mind and other ideas to show...
Regimes come and go, but human beings live on, and their values, strivings, search, aspirations, spiritual development and falls. etc etc... - remain.
It's almost as if you'd say that Shakespeare wrote 'King Lear' because he was pissed by monarchy and wanted to show how rotten it became. Nobody would say such nonsense. Then why on earth people used to assign label of democratic 'truth seeker' to every artist from socialist country?
(btw, here is English text of 'Roadside Picnic'