Jul 24th 2008 2:51AM In Blizzcon hunter panels the devs commented that:
"At Blizzcon Blizzard said that Beastmaster SHOULD do the most damage of the hunter specs because the pet is the most at risk."
Just google that and you will see different forum posts quoting it. Not sure if it can be found anywhere on "bluetext" since it was a verbal comment.
It kinda makes sense: you want best dps you have to be sort of a glass cannon and being a BM in raids and keeping the pet alive is definitely harder than keeping your character alive.