While I admire and am grateful for your sentiment on this, if torture did yield "absolutely vital information", the party that uses it would vanquish those who didn't.

The fact that we still wonder about this question may indeed prove that it's wrong from a utilitarian point of view.

That assumes that torture which reveals reliable information doesn't have significant bad effects. For example the police could put away more criminals if they could just torture anybody, but then nobody would ever risk talking to the police, which might mean crime would go up.