Aye, I don't use that scroll for it's debuff, I use it for it's interupt, as Elvan said. It's great on raids because it's got a 10 second recast and a 30 second duration. That means that we can keep the mob interupted indefinetly, which is great on caster mobs or mobs that stun the MT. I realize that the interupt probably doesn't last for the 30 second duration, but even still, an interupt every 10 seconds is pretty good if you ask me. Try spamming it between your other arts on raid mobs like Zalek in CL, your MT will love you for it. Anyway, IMO it's welcomed utility for us assassins, a class that has very little.