The reality of death defeated is not in dispute. The INFALLIBLE doctrine of Original Sin doesn't deny it.
The EO rejection of original sin is a recent innovation of theirs. From what I can tell, it traces back to their 19th century anti-Latin movement (they have always been ant-Latin to some degree, but it got really rabid at this time). They pretty much chucked anything that they thought seemed Western--this included original sin, since the theology behind it was primarily developed by St. Augustine. It may also be related to their revulsion towards papal definitions, in this case that of the Immaculate Conception (since they wouldn't attack the holiness of the Mother of God, they attacked the concept of original sin, which they had come to see as "Western.").
But they used to teach the Catholic understanding (just like they did with indulgences, satisfaction, etc.). For example, at their Synod of Jerusalem in 1672, they taught the following relating to infant baptism. Note the parts in bold--how is this different from the Catholic position? They teach that infants need to be cleansed of original sin to be saved and that original sin makes one liable to eternal punishment.
Synod of Eastern Orthodox Churches: Jerusalem, 1672
Decree 16
We believe Holy Baptism, which was instituted by the Lord, and is conferred in the name of the Holy Trinity, to be of the highest necessity. For without it none is able to be saved, as the Lord says, “Whoever is not born of water and of the Spirit, shall in no way enter into the Kingdom of the Heavens.” {John 3:5} And, therefore, baptism is necessary even for infants, since they also are subject to original sin, and without Baptism are not able to obtain its remission. Which the Lord showed when he said, not of some only, but simply and absolutely, “Whoever is not born [again],” which is the same as saying, “All that after the coming of Christ the Savior would enter into the Kingdom of the Heavens must be regenerated.” And since infants are men, and as such need salvation, needing salvation they need also Baptism. And those that are not regenerated, since they have not received the remission of hereditary sin, are, of necessity, subject to eternal punishment, and consequently cannot without Baptism be saved. So that even infants should, of necessity, be baptized.
Moreover, infants are saved, as is said in Matthew; {Matthew 19:12} but he that is not baptized is not saved. And consequently even infants must of necessity be baptized. And in the Acts {Acts 8:12; 16:33} it is said that the whole houses were baptized, and consequently the infants. To this the ancient Fathers also witness explicitly, and among them Dionysius in his Treatise concerning the Ecclesiastical Hierarchy; and Justin in his fifty-sixth Question, who says expressly, “And they are guaranteed the benefits of Baptism by the faith of those that bring them to Baptism.” And Augustine says that it is an Apostolic tradition, that children are saved through Baptism; and in another place, “The Church gives to babes the feet of others, that they may come; and the hearts of others, that they may believe; and the tongues of others, that they may promise;” and in another place, “Our mother, the Church, furnishes them with a particular heart.”
Now the matter of Baptism is pure water, and no other liquid. And it is performed by the Priest only, or in a case of unavoidable necessity, by another man, provided he is Orthodox, and has the proper intention to Divine Baptism. And the effects of Baptism are, to speak concisely, firstly, the remission of the hereditary transgression, and of any sins of any kind that the baptized may have committed. Secondly, it delivers him from the eternal punishment, to which he was liable, as well for original sin and for mortal sins he may have individually committed. Thirdly, it gives to the person immortality; for in justifying them from past sins, it makes them temples of God.
Is truth relative?