Neither stack.

Both evasion and critical strike work separately.

When you have 3 abilities:

1: 70% chance to deal 200% dmg

2: 50% chance to deal 200% dmg

3: 50% chance to deal 250% dmg

Then you have 2^3=8 different results:

1: 100% dmg (1 no, 2 no, 3 no)

2: 200% dmg (1 yes, 2 no, 3 no)

3: 200% dmg (1 no, 2 yes, 3 no)

4: 250% dmg (1 no, 2 no, 3 yes)

5: 300% dmg (1 yes, 2 yes, 3 no)

6: 350% dmg (1 yes, 2 no, 3 yes)

7: 350% dmg (1 no, 2 yes, 3 yes)

8: 450% dmg (1 yes, 2 yes, 3 yes)

The chances are separated accordingly:

1: (1-0.7) * (1-0.5) * (1-0.5) = 7.5% chance

2: 0.7 * (1-0.5) * (1-0.5) = 17.5% chance

3: (1-0.7) * 0.5 * (1-0.5) = 7.5% chance

4: (1-0.7) * (1-0.5) * 0.5 = 7.5% chance

5: 0.7 * 0.5 * (1-0.5) = 17.5% chance

6: 0.7 * (1-0.5) * 0.5 = 17.5% chance

7: (1-0.7) * 0.5 * 0.5 = 7.5% chance

8: 0.7 * 0.5 * 0.5 = 17.5% chance

(total = 7.5 + 17.5 + 7.5 + 7.5 + 17.5 + 17.5 + 7.5 + 17.5 = 100%)

So you have a very low chance that you will not critical strike when having these 3 abilities... however you have a very high chance (from 5 til 8 = 60%) that you will critical multiple times.

For evasion it is exacly the same...

But what if you evade one attack two or three times?

That doesn't matter. You will end up with the exact same thing as when you evade it only one time.

So for evasion chance you have:

100 - (1-(Chance of Ability 1 )) * (1-(Chance of Ability 2)) * (1-(Chance of Ability 3))

100 - (1-0.7) * (1-0.5) * (1-0.5)

100 - 7.5

92.5% chance to evade.

This calculation works for chances between 0 and 100 ofcourse.

When having a chance below 0 or above 100 the calculation is a bit messed up so you have to cap them at 100.

Oh and anything below 3% for critical strikes doesn't work since it uses a rounding system unlike evasion. 3 goes to 5 and 2 or lower means 0.

Thanks for the info edo494.

Are you serious?