Dear Friend,
Actually, there have been Orthodox saints and teachers who have believed in Purgatory!
St Peter Mohyla, Metropolitan of Kyiv, Halych and Rus' in the 17th century included Purgatory as an article of faith in his Catechism. This was expunged by the Orthodox Patriarchs at Jassy who otherwise approved his Catechism.
Nonetheless, Mohyla insisted that Purgatory be included in his Catechism as taught within his Metropolia. This was also accepted by the Kyivan Orthodox saints of the "Baroque era" such as St Dmitri of Rostov and a number of others who were trained at Mohyla's Academy.
In addition, the Immaculate Conception of the Mother of God was also taught and venerated highly by the Orthodox of the Kyivan Church where there were Brotherhoods of the Immaculate Conception very much akin to the contemporary Confraternity of the Immaculate Conception, promoted by the Marians of the Immaculate Conception - of which I am a proud member.
Fr. George Florovsky even criticized the emphasis that the Orthodox Mohyla Academy placed on the Immaculate Conception right into the 19th century.
So what I'm saying is that there really is no uniformity on such issues within historic Orthodoxy itself, let alone within the Eastern Catholic Churches.
Alex