In reply to jon:
Completely impossible, but it would be wonderful to interview each of these people just as the decided to ski, moment before the avalanche, just afterwards and then a few days later. Impossible, yes, but it would allow a window into the minds, and why they ignore such obvious signs. At an avalanche seminar I went to years back, the prof. giving the lecture said it was a fine line between saying yes and saying no, and it came down to the self-belief in the person, and their abilities. A confident, outgoing person might be able to ski medium risk slopes, because they are light, fast and relaxed, while a less confident person, might turn heavily, less fast and therefore trigger and avalanche. The confident person might be able too out ski said avalanche while the less confident person might panic freeze up and be buried. It’s all hypothetical, a high risk slope will take all, and the line between confidence and arrogance is very fine. The dynamics of the group are also heavily responsible for the outcome, with may be people with knowledge not been taken seriously or refrain from speaking out because of ridicule, while the more dynamic members of the group might ignore their shy protests, hoping there selfish arrogance will pull them through, almost certainly at the expense of certain members of their group. This is all hypothetical however!
At the same avalanche seminar one of the Davo’s avalanche’s pointed out that 65% of avalanche victims in Sveits were guided parties. It must be very difficult for some people to observe guides going out, and having to stay back at home. Local knowledge is everything, and a person who knows the landscape might get away with it (Might!), while a new person might not. Guides come in many shapes and forms, most well trained with mountains of experience, but also some have admitted in private they after all those years still they find avalanche assessment difficult to near impossible.
The conditions you described seem to me very obvious to me.