Actually, negative powers don't exist, while a fractional power is exactly what gives you a root
Fear attack probability
1 - (1 - Base probability)^0.8
modifiable parameter <Fear_ProcFactor>0.8</Fear_ProcFactor>
Stun probability
1 - (1 - Base probability)^3
modifiable parameter <SleepingStrike_ProcFactor>3</SleepingStrike_ProcFactor>
even the base probability there is calculated the same way
with equal health ratios of the stacks, the blindness probability (for example) will be 0.5, while the fear probability will be 0.17