(I'm taking for granted, in this question, that all four Marks are necessarily present until the end of time in the Church.)
In his response to the joint Catholic-Orthodox declaration, Metropolitan Philaret of the ROCOR states that union with Rome is only possible if "they accept the Orthodox Faith as it is maintained until now in the Holy, Catholic, and Apostolic Church." 
I found it interesting that there is the absence of the mention of any mark of Oneness or Unity, which, I would think, his eminence would certainly agree belongs as one of the Four Marks of the Mystical Body of Jesus Christ, as stated in the Niceno-Constantinopolitan Creed (emphasis mine) :
[We Believe in] one holy, catholic, and apostolic Church
Of the Mark of Unity, the Catholic Encyclopedia says that :
The marks of the Church are certain unmistakeable signs, or distinctive characteristics which render the Church easily recognizable to all, and clearly distinguish it from every other religious society, especially from those which claim to be Christian in doctrine and origin.
[the Church which has Christ for its founder] must unite its members in unity of doctrine[...] in unity of worship[...] and in unity of government.
This, to me, seems entirely reasonable, as without this kind of unity, there is only the "spiritual unity" claimed by Protestants, but they ostensibly have little unity at all, even within a single denomination.
Therefore I am asking that, if the Eastern Orthodox church is the one-and-only church founded by Jesus Christ, how does it manifest the Mark of Unity? The OrthodoxWiki does not have an article on either the Four Marks, or of Unity as a Mark. It seems to me that they do not possess it, on account of the multiplicity of churches within that communion, not all even being in communion with one another, and not all being recognized by one another.