Base on the data gathered by players from iCBT1 and kCBT3, im able to plot the Critical Rate vs Actual Critical Rate graph, and it appears to be a linear graph. (X-Critical Rate, Y-Actual Critical Rate)
2 of the formula are as below:
y = 95(X/175 - 1)
Character Level: 184 (Monk), Monster Level: 185 (Rambear), Crit Resist: 30, Crit Rate: 317, Actual Crit Rate: 85% (Info provided by the tester are limited and incomplete, the formula is questionable. http://www.tosbase.com/database/monsters/47462/)
y = 12(X/26 -1)
Character Level: 119 (Quarrel Shooter), Monster Level: 117 (Chronodog), Crit Resist: 26, Crit Rate: 196, Actual Crit Rate: 72% (according to the tester, the monster named Chronodog with 26 Crit Resist, located at MageTower 3F, monster record not found from ToSBase.com, but found a monster named Arma with Monster Level 119 and Crit Resistance 26 instead http://www.tosbase.com/database/monsters/47394/)
This Section had proved to be wrong
By factoring in Monster Critical Resistance, im guessing the formula is very close to this:
Actual Crit Rate = (Monster Level / 2) * ((Crit Rate / Crit Resist) - 1)
Assumption of Crit Resist proved to be wrong and does not scale with Monster Level
From the formula above:
Y = 95(X/175 - 1) = (19 / 35) * (X - 175)
Y = 12(X/26 -1) = (3 / 7) * (X - 26) = 0.4286 * (X - 26)
Hence, we can conclude the Critical Rate Formula:
Actual Crit Rate = Variable1 * (Crit Rate - Variable2)
*Variable1 believes to be a constant and different for each of the class
*Variable2 believes to be Monster’s Crit Resist
Actual Crit Rate = N * (Crit Rate - Crit Resist)
For Quarrel Shooter, N is around 0.4286
For example:
A Quarrel Shooter having 200 crit rate and the monster having 50 crit resist
Actual Crit Chance = 0.4286 * (200 - 50) = 64.29%
Crit rate to actual crit chance ratio = 1/0.4286 = 2.33
After deduction of crit resist, every 2.33 crit rate will improve the actual crit chance by 1%
Buff that affect Crit Resist - Zalciai (Krivis)
Lv5 -(12+SPR0.8) Crit Resist, +(37+SPR) Crit Attack, 38s, 20s cd
Lv10 -(20+SPR0.8) Crit Resist, +(69+SPR) Crit Attack, 58s, 20s cd
Lv15 -(28+SPR*0.8) Crit Resist, +(100+SPR) Crit Attack, 78s, 20s cd
(Attributes +9sec, +48 magic amplification)
Buff that affect Crit Rate - Monstrance (Priest)
+((DEX/10)*3+10)DEX, 20s, 23s cd for every levels
(Attributes +5sec)
Reference:
http://forum.gamer.com.tw/C.php?bsn=19840&snA=740&tnum=2
Reddit Discussion:
20160406 Update:
Actual Critical Rate = (Critical Rate - Critical Resist) * (42 / Character Level)
Source: Confirm by recent kOBT patch note on March 24 https://www.reddit.com/r/treeofsavior/comments/4bqxg5/ktos_324_weekly_patch/
Other Source: Critical rate formula (iCBT2 updated)