I'm afraid that analyzing those disasters in terms of the _specific_ mechanical failures misses the point. It's possible to spend a project's entire budget, and go profoundly over budget to the point of complete failure, by trying to find and resolve each individual bug as it turns up. I'm afraid that the frequency of space shuttle failures was _amazingly_ low considering the flaws in the overall manufacturing and design process, and I do applaud the individual engineers and inspectors who did their best to keep those craft alive. It seems to have been a constant, hammering refrain of "we have to change this bit to work with that other bit which no one could have foreseen", or in the case of the O rings, "now we cannot launch in cold weather". It's extremely expensive, and demanding, to keep any project alive with that sort of segmented design from conflicting designers and manufacturers, funding turf wars, and scattered manufacture. From my personal systems and international work, it's a _nightmare_.
Pointing out that Dream Chaser would not have that particular failure is irrelevant to the flaws that create these kinds of failure modes of interlocking systems. These failure modes kept playing out for the basic Shuttle design in equipment failures, in launch delays, and in several cases, in the deaths of all astronauts aboard. So I'm afraid that focusing on preventing mechanical disasters like the O ring needs to go further upstream, to the political process.