You're having a difficult time finding this out because the Orthodox Church has not and will not make a unified definitive statement of "validity." Even the term "valid" isn't a favorite vocabular word of Orthodox bishops and patriarchs. The old addage in Orthodoxy is "we know where grace is, not where it is not." So the short answer is, nobody knows.....
My priest has told me on several occasions that he feels the Catholic Church has solid apostolic succession and grace-giving sacraments. He told me that my baptism, marriage, confessions, and spiritual time there were all significant, viable, and meaningful. But they lack that fullness.
Being Orthodox is about "right teaching," not just looking at the sacraments as "legit" or phony.
The Catholic Church put the kybosh on the Anglicans in Apostlicae Curae in the late 1800's with Pope Leo XIII. The CC likes to declare who is valid and invalid. The Orthodox focuses inward to what they know as sure as the sun rises. And we know without a shadow of a doubt that the bishops of our Church have valid succession.
Succession is not terribly important if wrong teaching accompanies it. And if you look at the "Old Catholic Church" and the Episcopal Church, they might very well have valid lines of apostolicity, but look at the terribly un-Orthodox, sinful, horrible teachings they regarding sexuality, gays, abortion, marriage, non-Christian salvation, synchretism, women's ordination, and a bunch of other things. Being the Church means right teaching, right faith, apostolic succession, the seven sacraments, and unity in oneness. Orthodoxy has all those things....