I think it is a good decision to maintain air of mystery with the White Beings/Space Jockeys by not explaining them too much. In case of PROMETHEUS, the film does what others have failed: show instead of tell. Too many films suffer from over exposition, and sometimes you can hear the audience groan and complains. With the wordless, beguiling, awe-inspiring introduction of the White Beings, audience is more willing to immerse themselves in the story. Having said that, the proposed scene where the Elder blesses the Younger Engineer should be included. It will pay off near the end where one of the Engineers ruffles David's hair as if to bless him....before he rips his head off.