It is difficult to rip a piece of webbing on body weight, unless it is being worked over a sharp edge or another rope. It is extremely difficult to break a climbing rope on body weight. It can be done while climbing, it has happened, but you have to allow new and special circumstances.
On most harnesses, even if the strap comes undone, you are still in the leg loops or as it begins to loosen you can notice it. And it does not always happen all at once.
Sometimes "redundancy" only makes for confusion and danger. In other words, sometimes redundancy can mask the fact that nothing is good. Or sometimes redundancy in a knot or the way a long piece of webbing is used masks the truth that nothing is as it should be. Sometimes redundancy can cause a sling to be cut by another sling. In this regard one anchor, one new non-locking biner, one loop of webbing is better than two or three locking biners and can be perfectly fine. "Redundancy" is not the primary directive when you want a secure anchor. Foremost, each piece needs to be suitable to stand alone with no redundancy necessary.
Knots in webbing require maintenance. As any knotted piece of webbing is used the knots begin to work themselves apart. This is more so the case with solid thick pieces on nylon that are not, for lack of a better word, "braided". Some tape over the ends can be used to measure where the ends should be, and as they start to work into the knot you can measure how far they have moved and retie them.
Allow time to look over your equipment and call to mind everything that happens and what could happen and test it out completely, either mentally or physically before actually using it.
This is a very sad story. I am sorry to hear about it.
The Mohonk Mountain House and the Mohonk Preserve have done a great job protecting the environment thus far, but ... it's all down hill from here http://youtu.be/9AU8fMo8v4k.