@Casper, your test throws Defense away. Ya know that stat that ARMOR gives? It also throws away all minimal parry numbers we do get. It's entirely possible that the stat itself suffers tremendous diminishing returns, or even what Kitru posted as a theory earlier in this thread. (Once at X Parry, you don't need anymore)

BTW, checking you on the Lodestone, shows your Abysmal 550 Parry rating. Why are you arguing in this thread when you are, by your own numbers, down by a 6% chance to parry? Isn't that 1% Damage Reduction? You are absolutely terrible how you terrorize your healers like that! SHAME ON YOU!
(See what I did there?)

I was in Turn 7 for 8 hours in the past 2 days,(16%! almost there.) and ran a ton of tests on both 494 Parry, and 627 Parry. Both times, I still had a very equal chance of parrying through the entire fight.
And if you want my anecdotal version of your test Casper, several of my runs with 494 Parry, I parryd more than half the time. So RNG can and always will be a huge factor.

The only meaningful change I had been able to see was swapping out my Noct Hoplon for my Leviathan Shield. Truth be told, adding in a Buckler is easily the most consistent RNG based mitigation we can ever use. I have a set of macros that use Shield Swipe before Fast Blade, Savage Blade and Rage of Halone. I averaged 1 Swipe per combo, with the Hoplon, but then I put on the Buckler, and instead was getting an average of 5. (I only ignored the Swipe when Halone's De-buff was about to fall off) This saved me a TON of TP, and boosted my damage by roughly 5% Since 3 Shield Swipe GCDs is more Potency than the full RoH combo. Testing like this has led me to consider skill speed, since it's TP cost, is quite efficient actually. I never fell below 400 TP, and all I do on Turn 7 is stand in the same damn spot with the Lamia boss...

Also, as to everyone again talking about this "glorious!" 2% number here, Please read! Over the duration of a 12 minute fight, 2% Damage is still only equating to at most 10,000 Damage taken. (Thats being very generous BTW) At worst, thats 5 GCDs, over 12 minutes. And my healers NEVER once knew about my gear swaps, even changing from the Hoplon to the Buckler. 2% is NOT huge people! 10% is Huge, 5% is useful, 2% is just unlucky, and statistically a wash.

It sounds like people here would rather sacrifice ilvl for parry, because of that 2% number, which baffles me.