I think you are misunderstanding my point on this one. If it procs and you parry right away, it may have helped. If it procs and stays up until it falls off (without a parry) or has to stack up to 3x before a parry occurs, it isn't doing jack-all for you. I'm not arguing whether or not it is usefull (I'm relatively sure it sucks even worse now than it did in wrath), but my point is that if it procs and you parry it may have done its job, whereas if it procs and stays up on you for long periods of time it definitiely is not doing its job.
While Mellvar insists that many procs are good, I disagree. The added parry percentage isn't high (200 rating), and it's gone once you did parry.