For there to be a heresy about the cross, there would have to be an orthodoxy about it. Michael Gorman argues that contentions over how Jesus saves lead to an inadequate grasp of what the Passion means and does.
Sometimes preaching in a lectionary church is like being Philip in Acts 8—the Spirit plucks us up and drops us where ever she darn well pleases. It is necessarily this way, certainly. Between the thematic requirements of the seasons of the church year and the sheer length of the four Gospels spread out over 156 Sundays, there is no way we can read all four in their entirety in three years. So, we skip stuff. Especially in Year B, as we try to mash the shortest Gospel, Mark, together with the other Gospel, John, together in some supposedly coherent way.