Не получается воспроизвести. Прокает, но чень редко...
Так же комментарий есть на WoWhead:
500 spell casts showed a 4.2% proc rate, so I think the proc chance is a bit lower. Also it procs on non healing spells so its not just based off of crit heals. I've seen it triggered off fort and divine spirit. :)