There’s many reasons for this.
The most important reason… Is that it’s just not that accurate. Take this for example:
On the right, we have our parse of a 360 potency skill, Full Thrust, then we have our Minimum + Maximum calculated. Min+Max/2 = Average damage of our parse. Damage in this game has a damage range of +-5%, or *1.05-*0.95 damage ranges. You know your data has reached “accurate” values if you do Max/Min damage and you get a number close to 1.1053.
Our parse has an average of 847.2166667 damage. This does not include Crits, as it would skew our data.
Then at the bottom, we have our expected damage which uses the current Damage Formula… Our Damage Formula gives us a value of 835.8588004 damage. Thats 1.01358826% less than what the actual number should be.
That’s the first issue with the damage formula. It’s inconsistent. Yeah, maybe back during Patch 2.0-2.2, the damage formula was accurate. But that’s mainly because our Damage wasn’t that high. Because the damage wasn’t high, this greatly caused in-game rounding errors. The formula we currently use only matches a certain data set which only fit both Dragoon and Black Mage damage, which used low-magnitude data. The lower the numbers, greater the worse rounding data will be.
The next issue, is that the Damage Formula uses something known as a “Correction Formula”. Instead of identifying a pattern of the linear scaling of Determination from level 1 -> 50 and beyond, our data simply starts from our base of 202. This correction formula was present in both Valkys original formula, EMX’s formula (which we use) as well as the Japanese Damage Formula.
This will cause MANY issues throughout the years as we go through more and more Expansion packs and level increases.