Here is a possible source to answer your questions:

https://www.mdpi.com/634100

If you read the article, or at least the conclusions, you can see that there are still gaps in scientific knowledge about dormancy. 

To your last question about successful dormancy--Weather patterns can bring less-hardy plants out of dormancy. I should note that hardy is a word used to describe both overall "toughness" or ability to withstand adverse conditions and a word used to describe ability to withstand low temperatures. A plant like an edible fig tree can withstand high heat, drought, and cold temperatures. In the South, they would says that it is hardy. However, fig trees do not typically do well in Michigan because of the temperature extremes during the winter months. Fig trees will break dormancy when temperatures go above 50F. When we get a week of warm temperatures in January--as we did recently--a fig tree will break dormancy. Most likely, fig trees will die back to the roots or die completely when temperatures plummet to 20F. If there was a slow cooling off, fig trees might go back into dormancy, but with the fast changes in weather--a 30 degree drop in a matter of hours--the processes happening in the tree cannot "react" quickly enough and the cells die. 

Dormancy can also be unsuccessful if a plant is exposed to chemicals to which it is not adapted (e.g. driveway salts), if it did root deeply into the soil before hard freezes, if it was planted in a location where it does not go completely dormant (e.g. next to a south-facing house foundation), if pests chewed on plant parts below or above the soil level, if the plant was weakened by lack of water/too much water, or if the plant was weakened by soil type or pH not at optimum levels, or if the plant has a virus. There are many, many factors to consider. 

In addition, many plant cultivars have been selected by breeders or nurserymen for their beauty, not longevity. As the consumer, it is important to read about different cultivars, or different "series" of branded plants, and determine which ones seem to be the most hardy based on gardeners' experiences. 

Here is another source that might be helpful:

A molecular framework for seasonal growth-dormancy regulation in perennial plants