In contrast to the many here, I think trailer is well made.
On first part we are witnessing the horror scenes that are typical part of all Alien movies. And because we already know (and accordingly expect) that, there is no need to mask it in some kind of suspense attempt to make events in the movie more exciting. This is only a frame for more important, second part of trailer - introduction of David/Walter through the song "Nature Boy", which metaphorically describes him with peaceful, melancholic tone as "...a very strange enchanted boy..." who is "...wandered very far... a little shy and sad of eye...but very wise...". As contrast to that song, we are visually introduced to whole bunch of horrifying events, what suggests us that he is somehow connected to all that savagery at "the end of his journey".
So with that combination of cold melancholic chant as "introduction" of David and horror visuals, trailer shifts nicely the tension of the movie from typical horror elements of Alien to sinister but perhaps consequently logical reasoning of one "very strange enchanted" character who seems to have his own agenda despite terrifying consequences this agenda might have.
