The typical knock on redemptive-historical sermons is that they are all basically the same. They start in the garden, quickly move through whatever text is being addressed and then make a beeline to show how Christ fulfills the types, shadows and promises therein.
R. L. Dabney has something to say about this single-sermon phenomenon in his Evangelical Eloquence. In addressing a similar concern, Dabney discusses why sermons should not attempt to be complete syllabi in theology.
These two results would then be inevitable: that there could be but one sermon in substance, and that this one sermon must remain for ever a bare syllabus. The hearers would therefore never gain a full and impressive view of any one point of Christian theology; they could never receive more than a barren smattering of sacred knowledge (112).
If every sermon was a complete doctrinal syllabi then each sermon would be the same, bare treatment. Dabney argues that in order for the hearers to be taught the whole counsel of God in its manifold richness, each sermon must bear the text’s distinctive focus. I think Dabney is exactly right.
I also think that the perennial criticism of redemptive-historical preaching is not altogether accurate. Granted, RH preachers tend to start in the garden. RH preachers are also quick to show how Christ fulfilled the types and promises of the Old Testament. But is that such a bad thing? Shouldn’t Christ, his work and its organic relation to all of Scripture be proclaimed in every sermon?
I’m no advocate of lazy preaching. Younger RH preachers, especially, have the tendency to write each sermon as the same sweeping view of the entire Bible. RH preachers need to be careful to demonstrate each passage’s unique place in the history of special revelation. This, however, does not necessitate that RH preachers eschew Christological connections. All preachers are duty-bound to proclaim Christ in all of Scripture. I’m convinced that failure to do so is failure to honor God in preaching.

Camden,
We most certainly need to preach Christ in all the Scriptures! William Still once said that whatever book of the Bible you neglect in your ministry is a part of Christ that you are failing to preach.