I've come to believe that it's just something that Blizzard programmers are capable of, while Square Enix programmers are not.
Things are never the same when you are processing thousands of something as opposed to one of something. And that is where Blizzard is superior.
As far as I've heard, FFXI was never such a real-time system anyway, so Square Enix probably simply don't have the expertise nor the experience.