This is the kind of "narrative resort" that serves you to make a story perfect but, if abused, gets boring fast. It's like throwing sand to an opponent's eyes; it'd give a great momentous advantage, but imagine doing it every time, making a habit of it at the start of every combat...
Sounds stupid, doesn't it?
Another example; remember the first Conan movie? Towards the end, when Thulsa Doom finds he can't re-kidnap the princess from Conan's hands, and fires a serpent like an arrow. Subotai jumps at the last second and stops the snake with his shield. Very exciting scene right?
Imagine the character begins stopping arrows directed to everyone, all the time, every adventure, just because he can... All the excitement of the act is spoiled and turns totally boring.
That's why I wouldn't grant such an impresive feat as a permanent trait, but as an unique event that happens on the fly, at the crucial climax of the adventure.
Well, just my idea...