Its the way the ability was designed. You have to be at 100% for an entire second before the ability can be fade otherwise it doesn't get removed. That's what I get from my understanding of the ability right now. I don't use it because of the way it was designed. PLD and WAR don't have to deal with a death mechanic at the end of its duration so why does a DRK need too? It's a flawed ability that needs to be corrected or changed entirely.