"But I understand that you are looking for patristics."
Indeed I am as I have yet to find any indication in the East that Baptism does something other than bring us into The Church, forgive our sins and make us "new" in Christ and when they say these things they seem to be presuming that since the Resurrection, membership in The Church is the sine qua non of theosis and it is within The Church that our restored potential for theosis must be pursued. Of course they don't speak of Original Sin, but I didn't expect them to. They do teach that through baptism we die with Christ and our descent into the water is a type of His descent to hades and our rising up out of the water like His Resurrection and thus we are thereby purified of our sins to that point. I think Orthodoxy would say that it is the Sacrifice on the Cross, the descent to the dead and the Resurrection which took care of any "spiritual death" effects steming solely from the Sin of Adam.
Indeed. This is why our (Christian) baptism is different from the baptism of St. John: it is an icon of the death and resurrection of Christ. But this is also why it is onto remittance of all sin, including that elusive "spiritual death effects" that dare not speak their name...