Though finding fault with a crew's choices is not something that I take pleasure in doing, I believe that such mishaps should be analyzed fully in the hopes that others can learn of successful strategies for avoiding disaster before they have to come up with the strategy all by themselves.
I have a few issues with the excuse that their mainsail was torn and therefore they hit the reef.
For starters, Llewellyn Reef is about 185 kilometers NE of their intended destination, Burnett Heads, about 120 km north of their rhumb line to Burnett Heads. How could they have drifted that far without realizing it? That is more than a day's worth of drifting.
One supposition is that they were relying solely on celestial navigation and they had not been able to obtain an accurate fix due to weather for the previous 2 or 3 days. That could explain it, though it implies that they had no backup GPS at all, something that seems a bit short-sighted nowadays. If they did have GPS, such a navigation error is worse than just serious.
If they had reliable navigation instruments and charts, whatever were they thinking? When the weather is against you and you have difficulty steering a course to your destination, it is usually prudent to just heave to until the weather improves. Having a number of sailing friends who have navigated successfully several hundreds of miles with no rudder, or a torn and unusable mainsail, and other such mishaps, I find it difficult to understand a torn mainsail as an excuse for running up on a reef several days off course from the intended destination.
I wish that more information was provided. For example, how long had they been sailing with a torn mainsail? I understand that in rough seas having a mainsail up is more comfortable than going without one, but why didn't they just pull the sail down and repair it? Did they have a spare mainsail, or a storm sail, that they could used until the torn sail had been repaired? Did they have needles, thread, and sail palm on board?
I find the report lacking in enough information to be helpful to other sailors, and I would hope that more information was forthcoming.