Well, I've worked on thousands of disc brakes during my 10-years at a shop. For the most part, 99% of them work great. It's just the rare case when someone forgets to tighten an QR or something breaks and the overhead caliper design has no built-in safety margin to deal with it. The ONLY ones I've seen failures that caused injury were of this type (other than rider-induced crashes).

With a caliper under the chainstay and track ends, you can even leave the QR completely loose and braking-action will just shove it forward into the closed end rather than out the back. I always strive for the design that works 100% of the time, even when there's a failure somewhere. Just because some boutique manufacturers didn't do their engineering background, doesn't mean they're crap, just that it may only be 99% effective. Do you want to be the person with the 1% situation that had a problem?