Can explain %attack mutiplicative and %total/boss damage additive?

What do you mean by that, can explain in simple Mathematics formula?

General Formula
weapon multiplier * (4 * primary stats + secondary stats) * (Weapon Attack / 100)

With % attack and boss/total damage
[weapon multiplier * (4 * primary stats + secondary stats) * (Weapon Attack * (1+%attack) / 100)] * [1+(%boss damage + %total damage)]



ex:
weapon multiplier = 1.2
primary stats = 300
secondary stats = 4
Weapon Attack = 200
%Attack = 100% = 1
%Boss damage = 50% = 0.5
%Total damage = 50% = 0.5


By the commutative law, the order of multiplication/division doesn't matter
(Weapon Attack * (1 + %attack) / 100) = Weapon Attack / 100 * (%attack)

weapon multiplier * (4 * primary stats + secondary stats) * (Weapon Attack / 100)=
base damage =
1.2*(4*300+4)*(200/100) = 2890

base damage * (1+%attack)=
2890 * (1+1) = 5780

base damage * (1+%attack) * (1+%boss damage)=
2890 * (1+1) * (1+0.5) = 8670

base damage * (1+%attack) * (1 + %boss damage + %total damage)=
2890 * (1+1) * (1+0.5+0.5) = 11560

%dmg adds to itself (boss goes here at well), %att adds with itself, but they are multiplied to each other to produce the end result.

It's all about balance:

assuming a clean character, 40% dmg isn't as good as 20% dmg 20% atk.

Easiest explanation I can come up with. If you have absolutely nothing, you are dealing 100% damage.

Let's pretend you have some separate gear with 20% boss, 30% boss, 5% attack, and 5% attack.

ex1:
If you have two sources of %boss, they will add to each other.
100%*(20% boss+30% boss) = 150% damage on bosses.

ex2:
If you have two sources of boss, and two sources of %att, they will only add to their own kind... then multiply each other... easily seen in:

100%*(20% boss+30% boss)*(5% attack+5%attack)=100%*150%*110%=165% damage on bosses

the wrong way:
100%(20% boss+30% boss +5%attack+5%attack)=160% damage on bosses (once again this is the WRONG way)




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To further explain tecul1's post....

two pieces of gear with 20% damage:
100%*(20%+20%)= 140%

(which is the same as 1 piece with 40% damage)

But if you have two pieces of gear with one at 20% damage and one with 20% attack:
100%*(20% dmg)*(20% attack)= 144% damage

The higher the numbers get, the more noticeable the differences will become.





TL;DR (overly simplified but still somewhat accurate) formula

100%* (Sum of all boss% and dmg% boosts) *( sum of all %att boosts)

Thanks guys, I fully understand now !