Spell Critical Strike Chance Bug (Not adding up)

[blackfire1]

What went wrong?
I have to off-hand catalysts. One has implicit 5% Spell Critical Strike Chance (SCSC) and affix exalted 128 %SCSC
The other has only exalted 134%SCSC

If I equip the first, my Spell Critical Strike Chance is 66%, if I equip the second it falls to 33%.

Screenshots (via a site like imgur) or video, if applicable
Video of me equipping the catalysts and stats changing!
https://streamable.com/3exq8y

Thanks!

[A_S00]

This is working as intended.

The implicit is added flat crit (i.e., it brings the base crit of your spells from 5% to 10%), but both of the explicit mods are increased crit (they multiply your base crit by 2.28 and 2.34, respectively). Think of it the same way you think of flat vs. % increased damage.

Your total crit chance is:

(5 + [added flat crit]) * (1 + ([sum of increased crit] / 100))

…so in order to be hitting 66% crit chance with the Crystal Skull equipped, you must have about 332% increased generic/spell crit elsewhere on your character, to bring you to a total of 560% increased crit. That way, your total crit chance is calculated as:

(5 + 5) * (1 + (560 / 100)) = 66

The second offhand has about the same amount of increased crit, but no flat crit, so your total crit chance is calculated as:

(5 + 0) * (1 + (560 / 100)) = 33

The numbers on your character sheet are rounded to the nearest integer, so the difference between 128% increased and 134% increased is getting lost in rounding error.

[blackfire1]

Wow that makes flat increases incredibly powerful.

Thanks for taking the time to explain the interaction!