[Guide] atk% or CD for your substats, a.k.a, why you should (almost) never have over 200% CD on your char

[Jaysinz]

What you need to do before using this guide
1 Go to the info page of any monster, write down the atk stats, let's say it's 800+1252. Then divide the 2nd term by the 1st term, you get 1252 / 800 = 156.5%. Add that to your tower boost, if you have 14% elemental tower and 10% from ancient sword then the final ATK% is 156.5+14+10=180.5%
2 Go to the info page of any monster, write down the CD stats for example 170% (this includes the intrinsic 50%), add that to your tower boost, if you have maximum tower then it is CD=170%+25%=195%
3 When you crit, the damage is calculated as follows
Damage = BASE_ATK * (1+ATK%) * (1+CD)
the ATK% and CD are the values we calculated in step 1 and 2.
Now the simple conclusion
Middle school math tells us, when ATK%+CD = constant = P
(1+ATK%) * (1+CD) <= (1+P/2)2
The maximum is achieved when ATK% = CD = P/2
What does it tells us?
1.When you rune your monster, the goal is always to even out ATK% and CD, as long as it does not reduce P.
In other words, 190% ATK% + 190CD is better than 180% ATK% + 200CD. When you find your CD to be much larger than your ATK%, you should switch some of your substats from CD to atk%.
Theoretically you should never have more CD than ATK%.
This is particularly true if you have low CR, since the damage you deal when you don't crit is solely determined by your ATK% (CD has nothing to do with it)
Damage = BASE_ATK * (1+ATK%)
2 Some players chase mindlessly after CD, reaching over 200CD on their monsters. Note that with 4th equipped CD, it is difficult to have 200% ATK% on your monster. It is better to switch some of the CD to atk%
3 Now you also know how to choose between Rage and Fatal sets, and why sometimes Fatal is better than Rage.
4 This also works for skills that based on HP and DEF, as long as the damage contribution from atk can be neglected. In the case of Kumar, his third skill received little contribution from his atk stats. To maximize the critical damage, you should try to achieve HP% = CD, or HP% > CD for survivability. Don't go for HP%<CD.
5 Note that ATK% is not the the sum of the atk% on your runes. It also includes the plain atk stats from rune 1 and the boost from your glory buildings.
6 If you have 180 ATK% and 200 CD, but the best you can do is switch it to 185% ATK% and 185 CD then don't.