I've done many tests making the change in the registry whilst monitoring my latency through the performance monitor, and I've come to discover that this "fix" is actually detriment to the game. My latency is always a good 20ms higher on average when using the "fix", and that's not to mention all the other detrimental affects it is having on your system.
Those features were put into Windows by people far far smarter who know more about networking than any of us. It is there for a reason and personally, I don't think you should touch it no matter what the circumstance. But again I can confirm it does not help FFXIV in the slightest, so please don't do it.