What is the proc rate of the special ability on Pauldrons of the Skeleton King

There is a special legendary shoulder called Pauldrons of the Skeleton King that has a chance to drop from Act 1 bounty bags. The special secondary on these shoulders reads: "When receiving fatal damage, there is a chance that you are instead restored to 25% of maximum Life and cause nearby enemies to flee in fear."

Since I play a hardcore character, this special ability piqued my interest. However, it would be nice to know how good the odds are of this item saving a character from death.

According to the forums, the chance is 25 percent. http://us.battle.net/d3/en/forum/topic/12284718438