In spite of not calling her Theotokos, the Assyrians do heavily venerate St. Mary, and the local parish has a special Dormition service every August 15.
By the way, I will confess to, in the past, before my Orthodox formation had really begun, Ireceived communion at the Assyrian church (actually before I knew better I took communion from pretty much,everyone, including the Episcopalians; their bread and wine had certainly not become the body and blood of our Lord as the,white wine they used gave me horrible heartburn; the Eucharist, if it's real, should not be able to cause indigestion; on the other hand I have known the Eucharist from the Orthodox Church to make me feel better). I will say the Assyrians have hands down the tastiest bread, perhaps owing to their Malka sacrament in which the ancient yeast is reused. The communion is followed by sweetened antidoron. Taking communion at the Assyrian church made me crave pizza. I can't say if it's a valid Eucharist or not, as unlike with the Episcopal church nothing unpleasant followed taking it, and alas I don't have a trans-substantiometer that can examine the substance of objects apart from their accidents.
In general the Assyrians are good people and I've spent a lot of time wrestling with the hypothetical question of how to restore communion between them, the Oriental Orthodox and the Eastern Orthodox. The Christological agreements with the Vatican and the reforms made by Mar Dinkha certainly suggest a common christology exists at least as far as the Roman Catholic interpretation of Chalcedon. The Oriental Orthodox also came to a similiar agreement with Rome. So really it seems to me the personal question about the veneration of Nestorius is the main dividing issue at present. In the 1990s the Oriental Orthodox nearly did a deal with them but it fell apart over the Coptic insistence that the Assyrians anathematize Nestorius in the liturgy; Mar Dinkha IV is opposed to liturgical anathemas as a general principle. Anyone who loves the Syriac Orthodox, as do I, will also love and care about the other Syriac churches, the Assyrians and Chaldeans, who actually use Syriac in the vernacular more than anyone else, and the Maronites and Syriac Catholics, and all the Nasrani churches.
For that matter, it's hard to be a lover of Syriac Christianity and not find the Mandaeans fascinating: they are the Aramaic speaking Gnostics who follow John the Baptist as their chief prophet, view Jesus as an imposter and the Holy Spirit (described in the feminine, as in St. Ephrem, a typically Semitic detail) to be evil, baptize every Sunday, use as the banner of their community a cross with a fabric drape called a durshan or darshan, follow astrology that appears connected with the ancient Chaldean religion of the Babylonians, and make use of sacred threads and other accoutrements that closely resemble Zoroastrianism.