Don't forget the high church Anglicans. Also, most Lutheran synods suppose that Mary remained a virgin (including in the delivery), but would hesitate to say that salvation depends on that belief (hence Dogma).
I have an old (100 year old plus) Baltimore Catechism at home. Not sure how it ended up there, but the interesting thing is that the Eastern Orthodox are not considered to be a valid Church because they "Don't have the Pope as their head". If I paraphrased that right. So the view that the Eastern Orthodox is a valid Church is not as settled in the Roman Catholic Church as some suppose. In the Catholic Answers website there was a lone thread on this issue that ended badly and had to be locked down, with the many posts going against the Orthodox being a valid Church.
The Church, then they are not part of The Church. They may well be good Christian assemblies, but they are not part of The Church.
Would a Protestant need to be rebaptized then if they wanted to join the local Orthodox church?
"I have an old (100 year old plus) Baltimore Catechism at home. Not sure how it ended up there, but the interesting thing is that the Eastern Orthodox are not considered to be a valid Church because they "Don't have the Pope as their head"."
100 years ago, Rome certainly held to that concept, and we that they were damnable heretics. In 1967 the mutual anathemas were lifted by the Pope and the EP. Since then we've worked out many of the issues which had heretofore divided us.
"In the Catholic Answers website there was a lone thread on this issue that ended badly and had to be locked down, with the many posts going against the Orthodox being a valid Church."
I'm not surprised. We have people even in canonical Orthodoxy who still think that Rome is the Queen of heretics but they are few and far between. Many, though not all, are converts, who, and I'll likely get flammed for this, carry with them a certain degree of the anti Catholicism of their former faiths.
" Would a Protestant need to be rebaptized then if they wanted to join the local Orthodox church?"
Depends on how they were baptized in the first place. Jaroslav Pelican, for example, didn't need to be "re-baptized"! :)