NakedPastor has a helpful reflection on Matt. 15:21-28, one of the harder texts of the New Testament for myself. Since reading Christopher Wright's The Mission of God (which you should read), my hermeneutic for reading the Bible has become very missionally driven, but there are some texts including this one that don't "fit." The fact that there are texts that don't fit is a good thing for me, keeps me from making my perspective THE perspective.
If you cling to a very high Christology then you might not like his approach. I tend to move toward a high view through a low Christology perspective.
Here's some exerpts:
This passage has been of interest among many New Testament scholars because it shows Jesus possibly being outwitted by a foreign woman. Does this passage advance the Gentile mission or embarrass it? What does this mean for women in the early church?and
I love this story because it exhibits his humanity… a man forced to come to terms with truth foreign to what he is already certain of. He has to adjust, or amend, his theology because of the arguments of this woman. Here, many scholars agree, is the seed of the early church’s mission to the Gentiles.Much like the Peter and Corneluius story, what we find here is that participation in God's mission means that both parties will be changed. Mission is not about us going to save them, but mutual deepening and mutual conversion of faith toward the work of God in the world.