I have found formal services of Anathematization, but only in Church-Slavonic and in 18th century editions of the Trebnyk. The texts assume that the "heretic" is actually present, which may be why it passed out of use - who would voluntarily attend such a service if he himself was to be the object of attention?
Bless, Father,
I suspect that you're correct. In a somewhat parallel instance, the Rite of Degradation of a Bishop has seemingly passed into disuse and likely for the same reason - unless the deposed bishop elects to present himself for the formal purpose of being degraded from office, there is little call for the Rite to be exercised. And, as we've discussed previously, the last publicly noted instance of that ritual being exercised was upon the submission of Bishop Prince Rudolph de Landis Berghes, memory eternal, to Patrick Cardinal Hayes at St Patrick's Cathedral in 1919.
Many years,
Neil
