I've sat back and watched people close to the event and armchair analysts have a discussion about this very tragic outing. So many things were not right about the entire activity and they started with the notion to take students and non-students out on a dive that would be considered "experts only" if on a ski slope.
The location conditions, the dive plan, the gas planning (or apparent lack thereof) the experience of the attendees all combined to make this a disaster. Poor judgement of the divers and the instructor were the key to the entire event. And once they were in the water things just went from bad to worse. Chad's decision to go after a diver was his choice, be it from sense of duty, lack of experience, narcosis, or protective instinct. His choice obviously would not be everyone's choice, but it was his and his alone.
As far as blame, yes the instructor carries a majority as quite frankly, he knew better than that. Bad vis, increased river flow due to flooding, new divers who are still working on their AOW, operating outside of recreational depths without adequate training, and the list goes on. Just one of those should have been the giant red light flashing in his brain, but for whatever reason it wasn't.
The other divers also carry responsibility as they chose to dive and they ultimately accepted the risk of the dive. Whether or not you agree, that they understood the risks or not, they accepted them when they hit the water in the group.
I have mixed emotions about the Hero/Goat argument around Chad. I know for sure I never would have hit the water with that dive plan, so I can't put myself in his shoes. Unless you can mentally say that you would/do accept the risks of that dive plan you can't understand the decision making process that went on for him to go after another diver. But I look at his decision to go after another a diver and say good on him, but then groan that he didn't have the proper equipment (and obviously training) that would have made this a good choice for him personally. And quite frankly I couldn't sleep at night the rest of my life if I was the person he saved. My dumbass choices should be mine alone, and I just couldn't deal with the fact someone died saving me from my stupidity. It's one thing to be saved from fires or floods where the fireman dies trying to save me. It's something entirely different when someone dies saving me from being stupid.
Chad was a very nice guy, one I will have fond memories of. We had several parking lot chats when our paths crossed and I liked his enthusiasm.