The diver ran out of air.
Equipment failures resulting in a OOA incident are very rare, although they do happen.
Sometimes, in busy dive centres, empty tanks get left on board.
Every agency teaches some form of buddy check to ensure that tanks are full. I have seen gauges reading as much as 40 bar (approximately 600psi) out of whack, which was a one-off in all the thousands of divers I have guided, but even 40 bar defective would show a half empty tank on the gauge, which would be unfit for regular diving.
OOA and air depletion excercises are taught by all agencies as part of their fundamental basic training. The waiver may indeed be poorly phrased, however how could anybody suggest that equipment that is fit for multiple dives or boat diving is somehow inappropriate for a single dive?
As Thalassamania pointed out before - back in the day we dived with equipment we did not have to sign a waiver for, on the understanding that we were trained to check it appropriately. That included making sure the SPG read zero when not under pressure, and all the standard checks that are still taught today - and my "day" was a mere 10 years ago.
Any diving death is tragic, of course, but it seems this one could have been prevented by the diver adhering to basic training standards. I wasn't there, I am not a lawyer, but suing over the semantics of a piece of paper to somehow ignore the implication that a diver was, in fact, responsible for their own death is symptomatic of the fact that in this day and age, nobody is prepared to accept their own repsonsibility for anything.
Ultimate repsonsibility for the dive is incumbent on the diver, not the paper they signed without ever reading it.
Sorry of that offends, but people need to start accepting responsibilty for themselves.
Safe diving
C.