Serge,
Fátima, ISTM, is beyond the scope of Eastern Orthodoxy's judgement as it took place outside the context of the EO Church, but again ISTM (not that I claim to speak for any Orthodox church) it's fine - it condemned Communism, not Russian Orthodoxy.
I think that is a very modern spin on the matter. I think it's pretty obvious that up until the necessary "ecumenicalizing" it went under after the "new springtime" of Vatican II, the universal understanding of the "Fatima messages" was that the Russian people were to be converted to Catholicism - arguably some form of Uniate Catholicism, but undoubtedly Catholicism (in the old school RC ecclessiology - a subject of the Pope.)
On this basis alone, I think at least a prudential judgement could be made by Orthodox believers on the origin of these apparitions (either demonic, human delusion, or both.)
That would be reading too much into it. What I mean is EOxy won't waste time dogmatizing about things outside itself - you'll never see a dogmatic council bother to condemn Hinduism, for example. Of course that doesn't mean you can't say Hinduism is wrong.
I would agree that it's highly unlikely an outright foreign religion, of itself, would receive some kind of treatment by an Ecumenical Council (some imagined, hypothetical Council of the future...which may or may not happen before the Lord returns, who can say?).
However, the lack of such a treatment has in large part to do with there being a lack of any need for such condemnations. It is a given, that all that is outside of the Orthodox Church is anathema. Concilliar anathemas exist, because there was a need for them. Why? Because there was genuine confusion as to what the true confession of faith on a particular topic was. Councils are witnesses to the truth - they underline it, and hopefully make things unambiguous for everyone. At least this is how I've come to understand the matter.
Now that I think about it, maybe such a Concilliar declaration is necessary - since there is profound confusion in our times about just what the Church of Christ is - more moderate (but incorrect) folks saying it exists in the seperated communions of heterodox Christianities... more out to lunch folks (very much in line with modern RC ecumenistics) saying it somehow exists even in infidelic and paganistic religions.
Seraphim