I don't think result oriented decision making is realistic. The question to me is whether Luke was the right pick at the time. If a prospect suffers some sort of injury or illness later on, it's not realistic to decide he was the wrong pick because of bad luck or circumstances. Just my thoughts. If you want to say that the outcome for Luke absent injury or circumstances shows whether or not NJ has good scouts that's reasonable to me, but there is a big range of that. If Luke is a 45 point defender who is amazing in transition that is still a great player, even if he is not a 60 point defender who is even more amazing in transition.
I will say that right now, it's hard to second guess the Luke Hughes selection. He had a great freshman season and was so young, that he could very easily have been in this draft in the conversation for first overall. My guess is that he'd be picked by NJ at two if MTL didn't take him. That's all on his own merit. I think the brother connection is a sort of tie breaker, where it's as fair as any other tie breaker.
I agree that posters can overrate the value of these connections but they aren't wrong that it matters to the players. Why do Vancouver fans keep suggesting a trade of Jack to NJ? It's don't think it's because they hope Jack will make Quinn play better; it's because they are concerned that Quinn will leave to join Jack and Luke when his contract is up. Jack was pretty explicit when he said he'd stick with NJ since they drafted Luke. Obviously, on some level it matters to him. In the past, the example of the Niedermayers is also an instance where it mattered to some degree. It's not a sole reason to do things but it shouldn't be completely discounted either as I see it.