The standards in regard to minors are in place for two reasons:
1) Most minors don't exhibit good judgement when left to their own devices and therefore should be monitored by an adult. There are many laws and regulations illustrating this outside of diving.
2) There has been some debate regarding the possible effects of diving on bodies that are still developing, so "acceptable" limitations are imposed.
Things I've just learned:
1) There WAS a hard bottom more or less within recreational depth.
2) Out of a group of divers that had both experienced divers and brand new, with only two dives, only two seemed to recall the concept of buddying up and doing checks themselves.
3) A diver in the deeper group had a problem, possibly splitting the DM attention between 3 groups, one at 60', one at 80' and one diving over a hard bottom. Presumably during this time is when the diver went missing.
4) One diver wasn't monitoring his gauges close enough to know what depth they hit during the dive and was relying on the max depth indicator to tell them what it was later.
I would think that if a group of people who knew each other came in to a shop and wanted to dive, that group would generally buddy themselves up since they know each other. I wouldnt expect the DM or shop to be responsible for naming the buddy pairs unless it was a boat full of strangers.
I would think that divers with only two dives post cert would still have the whole "buddy concept" fresh in their minds. Usually people don't start disregarding that until they've gotten a bit more experience and feeling confident in their abilities as individual divers.
With the new information regarding the bottom terrain, it would seem the missing diver had to work to get to 346'. He didnt just pass out and drift down the wall.
Another diver has a problem and started ascending. The DM now has 3 groups to keep track of and I would expect that his attention would be on the diver who had a problem and started an unplanned ascent.
There are 3 divers who are at a minimum 20' - 40' above the rest of the group, who would have been looking down to see the coral, fish and terrain on the bottom, yet none of them noticed the other diver go missing.
At least one other diver in the group failed to track their own depth during the dive, because they had no idea how deep they'd been since the max depth indicator needle didnt work.
IMO, a LOT of things went wrong on this dive and I have a hard time laying them all at the feet of the DM.