Yea I had 'heck' with this issue, but what they say is totally true. Overtime [and it takes a LOT of times], the puppy will start to learn that biting = my master leaves. You have to make sure you're like..completely out of reach. Not just a couple steps away. Also make the 'absence' longer than a couple of seconds. Also be REALLY consistent. My puppy, over time, started to react to my leaving, and I got to shorten my 'absence times'
In addition I think they're right about the adult dogs. Over time the adult dog will teach the puppy proper behavior. my neighbor has an older dog that always kind of disciplined the younger dog as to what to do. I think your older dog might be the 'nicer' type, but I'm guessing that sooner or later they will 'burst', AKA growl or nip back. Though it sounds nasty, I think its a GOOD thing you have an older dog to teach the puppy this!