I agree. Diving with a large group can be riskier in general just because the more divers there are the harder it is to keep track of everyone, but it is incumbent on every diver to watch out for his/her own safety. That is what getting certified is all about.Anyone with a c-card is supposed to know how to watch their depth and time and stay out of deco. No diver should ever be putting their life in someone else's hands.
Diving deep on a second dive after getting a significant N2 loading from the first is dangerous; he should have stayed shallow or called the dive when he saw the way things were going. My wife I have had to do that, and on one occasion when we stayed shallow while the rest went deep the other divers' computers showed skipped deco stops. Not good.
Is his wife OK?