It's hard to see how her death can be disputed by Roman Catholics considering the words of Pope Pius XII in the very document by which he dogmatically defined the Assumption. Ther Pope says, at least five times, that the Mother of God DIED. Catholics can wriggle out of this and say the Pope has no idea what he is talking about. They will claim that only the very small paragraph where the Pope defines the Assumption is binding on them. As for the rest of the infallible document it is erroneous, the Pope is wrong. I personally find it hard to belioeve that any Catholic could claim that the Spirit protected the Pope from error over one small paragraph and yet allowed him to teach erroneously five times in the same magisterial document!!
It would, btw, be quite impossible for Eastern Catholics not to believe that the Mother of God died without doing an act of violence to their own sacred Tradition. The iconography, the hymnography and the oral Tradition all teach that she did in fact die.
People like to say that the Apostolic Constitution "Munificentissimus Deus" by which Pope Pius XII established the dogma of the Assumption in 1950 makes no mention of whether Mary died or did not die.
This is inaccurate. One only has to read the document to see that the Pope teaches that she died. For example, he says:
"Thus, to cite an illustrious example, this is set forth in that sacramentary
which Adrian I, our predecessor of immortal memory, sent to the Emperor
Charlemagne. These words are found in this volume: "Venerable to us,
O Lord, is the festivity of this day on which the holy Mother of God
suffered temporal death, but still could not be kept down by the bonds of
death, who has begotten your Son our Lord incarnate from herself."
"As he kept you a virgin in childbirth, thus he has kept your body incorrupt
in the tomb and has glorified it by his divine act of transferring it from
"They offered more profound explanations of its meaning and nature, bringing
out into sharper light the fact that this feast shows, not only that the
dead body of the Blessed Virgin Mary remained incorrupt.."
"she has received an eternal incorruptibility of the body together with him
who has raised her up from the tomb.."
"What son would not bring his mother back to life and would not bring her
into paradise after her death if he could?"
These quotes from the papal document defining the Assumption are proof that the Pope taught that Mary died and was buried in a tomb and from there she was resurrected by her Son.
So there we are.... There is the "magisterial document" we are asking for.
"MUNIFICENTISSIMUS DEUS" Pope Pius XIIhttp://www.ewtn.com/library/PAPALDOC/P12MUNIF.HTM