oddly enough you say that, but in truth the 100 kt point is very telling, I always say 100 kts, 30 seconds, now that is my airplane, empty or full, a 747.
I say this because if I have not reached 100 kts by 30 seconds I know two things, either I have incorrect power set for the weight, empty or full, or I have a significant speed reduction, ie dragging brake, etc. Either way I know from time on type I may reach V1, but never VR in the confinements.
Rules of thumb are just that, a gross error check, but they serve the purpose to put doubt in your mind, and if I reach 100 kts and I am 20 seconds, I am stopping, if I reach 100 kts and I am 28 seconds I am very very observant. It cast doubt, and thats exactly what a rule of thumb is intended to do. It alerts you to impending disaster, and you react accordingly, I reach 120 and it still looks odd, I am now stopping.
beyond that, my options are limited.
Thankfully this has always carried me through, I have reached V1, and subsequently VR, albeit sometimes pretty far down the available surface, but it has worked.
I can say, from years of flying heavy aircraft, go oriented is a mindset, but the reality is always that the spread between V1 and VR can mean you may make V1, but never VR.
That is a reality I hope I never encounter.
I can well imagine what these guys saw, I hope to never see it, but I feel that gross error checks have their place, and it is exactly this scenario.
I cannot help but think that reliance on technology has pushed the gross error checks to the side, which may be a shame.
I would never dare to criticize the the crew involved, they acted on what was the information of the day. They now live and die by that inputted information, they undoubtedly believed in what they did at the time. I understand they were high experience, well established crew, unfortunately, as previously stated, you are as good as your last flight.
I suspect that training has shifted to reliance on given information, and it is very easy as crew to take face value information as gospel, I have seen it on occasion, the flight plan gives you a fuel, OK put it on, did you check it vs time and burn? no, it was on the plan, but they realize that they will never make destination.... after they depart.
A gross error check would have caught that, average burn VS FP fuel, for your weight.
We as crew are the final check, not dispatch, not load planners, because guaranteed when the flight goes all wrong, none of them are to blame.
The CPT signs the book, and will be fully accountable, and thats why in my back pocket I always hold a few gross error checks, they may seem old fashioned to those trained on glass, and fully reliant on given information, but they have served me well so far, and I have seen no compelling reason yet to give them up.