There are actually many saints that Eastern Catholics venerate that are (technically) Orthodox saints. St. Seraphim of Sarov, St. Theophan the Recluse, and St. Ignatius Brianchaninov come immediately to mind. These are all men who were not in canonical communion with Rome when they died, but who are honored as saints among Eastern (Byzantine) Catholics, and their writings are held in the highest esteem.
Lest we think that canonical communion with Rome is necessary for sainthood, I would point out that St. Gregory of Narek, whom Pope Francis declared a Doctor of the Church, was not in communion with Rome at the time of his death.