Why is Abraham considered to be THE example of a man of faith in Scripture? Sure, he leaves his homeland when called by God. But there is good reason to believe that at that point he sees YHWH as simply another of his ancestral gods. And the story of his willingness to sacrifice Isaac in Genesis 22 is a powerful story of faith (trust). I still can't get my head around why God would have made such a seemingly barbaric request of him. Perhaps it represents a clear break from the pagan practices of his past?
But then you have TWO episodes in which, in order to save his own skin, Abraham allows his wife to be used as a concubine. I don't understand such cowardice from THE man of faith.
On another note, I have done extensive studies of David, and I always come away from them wondering, "How could this guy be called 'a man after God's own heart'?" He was brutal. He was a sexual predator at times. And while the psalms certainly reveal a heart that could be SO in tune with God, they also reveal a man who longed for revenge.
Maybe all of this is intended to show us that the focus should not be on these men, with their spiritual titles. When we hold them up to their titles, they leave us disappointed. So it seems to me that we would be better served to be directed to the God of love and mercy and grace, who chose to embrace these sinful men and use them for His purposes.