paul from cl.,
Your presentation of the JW doctrine was unusually clear, that's probably why I felt like picking it apart. :)
But you got my drift I suppose: if that's the core of the Christian faith, why is it not simply taught in a similar way at least somewhere in the whole Bible? Why the need to construct an unscriptural doctrinal argument with unscriptural notions, even if you can fit a few verses here and there (preferably out of context)?
JWs would make exactly the same point about "orthodox" syntheses like the Trinity doctrine: no matter how many Bible texts Trinitarians can quote to back it up, the fact remains that the doctrine as such is not taught anywhere in the Bible. This is actually their strongest (negative) point. But ironically they don't see that this applies equally to most of their "positive" doctrines, including the "ransom sacrifice," "perfect Jesus" recovering what "perfect Adam" had lost, the "scales" of divine justice, and so on.
dissed,
I think you are trusting the WT too much on at least two assumptions: (1) that the notion of "ransom sacrifice" in some form was common to most if not all early Christians; (2) that doctrinal development in general emanated from the "apostles in Jerusalem". The whole Pauline corpus (especially Galatians) opposes this idea, although the book of Acts promotes it to an extent. But the christology of Acts is fairly different. In the discourses of Peter, for instance, Jesus' death is not described as a ransom (it is noteworthy that Luke drops the ransom logion, Mark 10:45) or an atoning sacrifice (let alone both!) but as the unjust condemnation of the "righteous one" who is vindicated by his resurrection and elevation to the right hand of God -- a completely different scenario.