A quick read from the Pray Tell blog on the Dormition-Assumption in both the Orthodox and Catholic churches.
The changes in the Roman Mass of the Assumption are of a magnitude scarcely noticed in typical Western liturgical circles, including those of a more academic bent. If there is any objectivity in the matter, Pius XII's liturgical changes will come under more scrutiny, at least at a scholarly level. Indeed, it is the inability to critically examine the liturgical changes of Pius XII that discredits much of the Traditionalist movement (in my eyes).
Back to our point, the significance of Pius XII's changes to the Assumption liturgy are hardly considered when discussing 20th century liturgical reforms. Whereas the encyclical promulgating the dogma of the Assumption showed some restrained in dogmatizing the particular Western tradition of the Assumption, in which Mary escapes bodily death and enters into heaven, the alteration of Mass texts pivots firmly to the West.
Assumption, however, has never meant exclusively the escape from bodily death. The Orthodox Church knows the feast as both Dormition and Assumption, depending upon how close a church was to Western Europe. In both cases, the falling asleep of Mary is commemorated. In the West, the Assumption was interpreted as both the falling asleep and preservation from bodily death. This said, three points ought to be noted,
1) The oldest tradition of the Assumption in the West commemorates the falling asleep of Mary, in continuity with the East.
2) The most reliable historical research confirms that the tradition of Mary's preservation from bodily death likely began in Gnostic circles in the West and was later appropriated by the mainline Church for pastoral reasons. (see Shoemaker's The Ancient Traditions of the Virgin Mary's Dormition and Assumption, 1st ed.)
3) The oldest texts describe Mary's death and then bodily assumption into paradise.
Pius XII's reform of the Mass of the Assumption broke with a genuinely universal tradition between Orthodoxy and Catholicism, in favor of a peculiarly Western interpretation of dubious theological merit and historical precedence.
In all of the movement to institute a comprehensive liturgical reform culminating in the Missale Romanum of Paul VI, restoring something more akin to the original Mass and its original prayers was never considered. This leads us to consider two interesting paradoxes.
For Traditionalists, the reform of the Assumption Mass immediately challenges their interests in preserving Tradition, in so far as it reveals their stated aims are subject to the papacy. This raises a host of ecclesiological questions the Traditionalist movement in the Roman Church has been unwilling or unable to answer.
For Progressives who see the Pauline liturgy as being more ecumenical, they are left having to reconcile how many of the final liturgical changes eliminated universal Traditions and express a peculiarly Western, and specifically Roman, understanding. The Assumption Mass is a case in point. For ecumenical as the Novus Ordo is made out to be, it is, in many respects, anti-ecumenism in so far as much of the ancient liturgical expression was jettisoned in favor of aligning liturgical prayer with later defined doctrine.
My sincere plea is that anyone genuinely concerned with liturgy, liturgical reform, and ecumenism begin asking some of these difficult questions.