There is a questline in Coerthas western Highlands that touches on this subject (MINOR SPOILERS just a little warning if you don't want to read about it before doing the questline) as you help a couple young Dragon hunters bag some kills, and that apparently big dragons come for the corpses of smaller dragons and they do this as an honour.

Also specifically states that ALL aevises were once people that partook of dragon's blood (so all of them in the stone vigil were once people, not just the ones you watch transform) and the question is raised why they would do this, become beasts..
But what if they don't? Not really?