http://lodestone.finalfantasyxiv.com...entry?e=342613

In short :
- It takes roughly +30 "crit rate" to increase your actual crit % by +1% on R45. This return may vary with dLVL, but would likely only decrease with increasing dLVL.
- There is a cap on Crit Rate % at 20%. We did not assess for a Crit Rate % floor.
- Crit Rate for R45 was roughly 11.2%. ~6% for an R55 mob