Key word is current, as in the action they are currently trying to perform. There's no debuff which prevents their next action, or anything like it, so you'd have to be landing the interrupt as they leap, if it's even possible, which I'm pretty sure it's not. Make a video and post it, but I'm still pretty sure you're just blowing your interrupt for no good reason, but then the only people we could really use it on are sages, healers, and other mercs/commandos.
Well maybe so, so I stand corrected than but I do use this ability religiously in my rotation and every time it is up I fire it off.
I was under the impression that it interrupts current action in meaning that whatever ability they use next it interrupts that ability because it becomes the current action performed and it doesn't make sense when you fire off a disabling shot when there action is already performed.
And I gave you pics from several matches that I was in but I am currently in the making of a video once I get enough footage and I look forward to posting it =)