Against L45 enemies your crit rate increases by ~1% for every +30 Crit Rate you have and the base crit rate is ~11%. Against higher level enemies it's lower and it is also assumed the potency of +Crit Rate goes down as dLevel increases. Crit rate is capped at 20%.
This means adding +Crit Rate is very inefficient as far as the rate of criticals goes.
Crit damage has a floor of 115% and a ceiling of 175%. These are placed after the actual calculation for crit damage and the formula is affected by dLevel. Against a L50 enemy your critical damage is ~120% and by dLevel = 4, your crit damage has fallen below or roughly to the 115% floor. This means when dLevel > 5, the initial points of any Critical Potency on your gear are essentially wasted. When dLevel = 8 (Ifrit), you waste the first 56 points of +Crit Potency before you get any effect.
The dev team clearly isn't aware of how mages work and they still struggle to make gear that mages actually want to use. The end game darklight mage items suck and every primal CNJ/WHM drop has only offensive stats. It seems obvious that whoever designs this stuff has very limited understanding of the game mechanics involved. I don't need to test the Garuda, Ifrit and Moogle wands to realize that their effect on my cures and buffs is between zero and marginal.Math and science do not operate the way you are trying to operate. If this was a scientific community, your reasoning woudl be labeled highly flawed. And it is. I'll repeat for like the 20th time, the dev team is aware of certain things that you are not. Instead of accepting this, and looking for where your knowledge could be lacking, you cling to now-dated tests that don't even test the thing you are arguing against.
If you want more detailed information about stats, I recommend you read this thread and the LJ posts by Kaeko you'll find there. He has a much better understanding of the actual math and testing methods, so you better ask him if you want to question the results.