My sense is that Luke does discuss the blood of the New Covenant in Luke 22. There are likely two traditions of the wording of the Last Supper in the NT and Luke's is close to Paul's in 1 Corinthians 11, not like Matthew and Mark that a scribal addition is more likely to have followed. More than that, Luke uses Servant imagery to discuss Jesus' suffering that places him in some kind of a substitutionary mode. The picture of washing tied to responding to Jesus also points to some kind of cleansing tied to Jesus' work in Acts. So the distance is not as great between paul and Luke as you suggest. Rather, Luke highlights who saves more than concentrating as Paul does on how it works as well. If Luke really was that different than Paul I do not think he would have included the remark he does to the Ephesian elders in Acts.