First off, I am new here. Thank you for this beautiful forum!
So what's the problem with the Catholic doctrine, then?
We don't like the wording of the dogma which leaves open doors for further developments such as the belief that the Theotokos never really died, etc.
I have studied Munificentissimus Deus
(Pius XII's 1950 bull that dogmatically defined the Immaculate Conception) in great detail. Michal, you are quite right that the ambiguity of document _could_ lead one to believe that Our Lady did not die. However, it is perfectly "acceptable" for a Catholic to believe in the Orthodox understanding of the Holy Dormition/Assumption. Personally, I believe as the Orthodox do, that she indeed died as she is mortal. Most educated orthodox Catholics I know agree. Our Lady's mortality, however, does not detract from all the veneration due to her as Theotokos/Genetrix Dei/Deipara etc.
I am still a cradle Catholic, but I find myself contemplating conversion to Orthodoxy all the time. Roman Catholicism is in a dire sort nowadays, as most all here probably know. The Novus Ordo was an inexplicable move with disastrous consequences (why did Paul VI have to go there?). It's liturgy by academics, not liturgy by revelation. I only worship at the Extraordinary Form or at an Eastern Catholic Divine Liturgy. At the moment I attend the DL since I cannot get to a Latin Mass. I love the Divine Liturgy because it is, of course, the unbloody sacrifice and a historic orthodox liturgy, but my spirituality is still very western. I respect the Eastern spirituality deeply (especially the profound Eastern veneration and love of Our Lady), but I still feel as if I'm in exile.
The real reason why I have not converted is because I love the classical Roman liturgy, the Roman Canon, and the Latin language. Still, I am so distraught at what has happened to the Roman Church that I just want to flee. Something tells me, though, that the Roman Rite will indeed survive this tribulation and emerge again in its ancient form. We will not only survive, but emerge with a vigorous liturgical orthodoxy. This is our iconoclasm, 1300 years later. I must trust that the Church will learn that the academy and social sciences are works of human hands that will never supplant the glory of orthodox sacramentality. I just don't know why we westerners are being tested at this time of history.