What you want is two or three people really in charge, where the individuals are empowered to say: "I am totally confused. If someone cannot explain what is going on to me so that I understand, I am starting shutdown procedures, immediately. Do YOU know exactly what is going on?"
Maybe you have to figure out a way to test people for unusually high aptitude at looking at mind-numbingly dull repetitive things over and over again, but then still being able to notice the aberrant ones. And then only put people in that job with unusually high aptitude there.
Or have people only do pretty short shifts at that task.
I'm pretty confident that this person wasn't unusually negligent, if you have most anyone doing that job hour after hour day after day they will lose the ability to flag the aberant stuff.
If an alert system is not perceived as highly reliable in directing positive action, then the humans involved will inevitably disable the alert system, either by pulling out a screwdriver or rewriting their mental rubrics to ignore the messages as noise.
Knight Capital is just the finance version of Three Mile Island and Deepwater Horizon -- the means to mitigate or prevent disaster were on hand, but the people in charge just dithered by the kill switch because they were confused. Well, if the people in charge are confused, that is a reason to start the emergency procedures.
People ignore repetitive things, but they usually notice when it changes. They can tell you that it's shaped different or explain how it sounds different from normal.
If this system made dissimilar transactions look very similar to the monitor, then it is to blame, not the idea of having a monitor at all.