"There is no indication throughout the story that you're actually helping Damian"
Well there actually is (or perhaps are) an indication that Talana is not so nice as you think she is. After you've brought back the crystal skull in Broken Valley and you obtain your pet, she says something like: "now you've got your own little pet and I've got mine... haha.. joke"
I only noticed it the second time I played, but Im sure there must have been more of those indications. Anyone else saw one?