4 more thoughts:
1. IMHO I feel that it is quite telling of the local dive culture when "blaming" that so little attention has been turned towards the "buddies". Same ocean buddies, apparently. Left the guy in a lurch, didn't surface to find him, didn''t do anything when reboarding boat or at roll call. And this thread's readership, hasn't focused their attention on these "poor" buddies either. Apparently too many don't take seriously "buddy" once they assume responsibility by diving together as such. The first guys I'd sue would be my errant buddies (but then, I wouldn't sue anybody anyway, if I had been the victim).
2. If it's true this was a "live-boat" (IMHO almost absolutely: too deep and rig security issues), did the boat drift down current or maintain it's position up current with screws turning/engines reving? Since I have never dived the rigs before, how do boats generally plan to recover their divers? Speculating only, seems to me like the plan would be drift down current, then as divers surfaced (they would hold position), the boat would approach and pick-up; boat would again drift, re-engage for pickup, etc. until all were aboard? Is this the general procedure? Was the boat following generally accepted pickup procedures for rig diving? And how did this victim diver miss that monster Eureka Rig in the drift anyway; even with failed attempts to ear clear, seems to me he would have necessiarially been scrambling to avoid running into pilings and cross-members? I speculate there is something more than ear clearing this diver is not admitting here. I suspect the victim diver should do some "soul searching" regarding his skills.
3. Even with air-powered dive alert horns, the open ocean quickly absorbs the sound. I've been on boats with 20-25 knot winds blowing and no one on the boat could hear divers a 100yards away blowing their air powered horns. In So.Calif fog like that pictured above, the local ocean is always flat and calm without wind. Boat couldn't hear the victim's whistle over the engines? (were the engines running?)
4. No such thing as blame when submerged, only solutions. "Be prepared."
After the fact, everyone argues some level of their own mortality. This incident had a favorable outcome. The real heros here is the Argus, the Boy Scouts, and the US Coast Guard. I think the Sundiver crew, customers, victim all ought to be giving their thanks and gratuities to the Argus, the Boy Scouts, and US Coast Guard. Always prepared.
All the best.