Here's a short but informative guide written by vinter888 of DN SEA forum on how damage reduction works in the game.
To show how damage reduction work. there is few groups of damage reduction
Defend and magic defend of a character, cappd at 85%. most obvious way is wear armor, int give Mdef, vit give def. so ****tail and genie that give int% and vit% indirectly improve def and mdef too. int class will naturally have high mdef by stacking int(sorc,priest,screamer,ml,art). so there is pattk/mattk by bosses as well, pattk reduce by def, mattk reduce by mdef.
Damage reduction by buff and defend buff on action. capped at 75%. skill included: iron skin, howl charging, ice/fire shield, heal of chakraEX, miracle relic, protection shell, fiery vortex, rolling attack,Eraser,mechanic mode.
Additional notes from Vaporizer:
Just wanted to point out that the damage reduction from skill action will not take effect on the hit that breaks the skill SA (unlike buff clearing skills, the damage from these skills, if any, will still take into account the buffs that were present on the character before being cleared by said skill).
Damage reduction by reducing boss attack(debuff). capped at 80%. 3 skill only in DN, taunting howl, Havoc howl and mecha bomber. it work by reducing the attack power of attacker. with the natural of these skill, it work wonder in map(BDN) have alot buff clearing mechanic
Elemental defend. capped at 90% skill included:conviction aura(light def), elemental aura(fire and ice def), blessing of light(light def). can reduce damage of corresponding element attack.
Transition Damage. exclusive skill of engineer.has own mechanic to reduce damage. it work by transfer away 60% (max level)of the damage received to alfredo. and this buff still work even the alfredo is not on field, as long the buff is there.
Phantom Guard, work similar as TD, but is transfer 22% (max level) of damage received to MP.
Defend buff with durability. skill included: Guardian force and bubble bubble. adsorb fix value of damage received.
A mathematical formula to show how they work together.
Raw damage x (100%-reduce boss attk) x (100%-def/mdef of char) x (100%-dam reduction by buff ) x(100%-elemental def) x (100%-TD) x (100%-phantom guard) - (defend buff with durability) = damaged received/hp reduced
if final value is negative value it mean 0 damage received cause adsorb by GF/bubble and still have durability remain to absorb next attack.
1. boss deal 1 000 000 raw damage, there is taunting(20%), HOC(50%), phantom guard(22%) and character defend 40%
damage received = 1000000 x (1-0.2)x(1-0.4) (1-0.5)x(1-0.22) = 187 200 hp reduced
2. boss deal 1 999 999 raw damage, there is havoc(60%),taunting, howl charging(30%), hoc and phantom guard. char defend 40%
hoc and hc is same group so 50%+30%, but is capped at 75%.
taunting and havoc is same group so is 20%+60%
damage received = 1999999 x (1-0.8) x (1-0.4) x (1-0.75) x (1-0.22) = 46 799 hp reduced.
3. boss deal 2 888 888 light elem raw damage, there is TD(60%), mecha bomber(36%), protection shell(24% def),MR(70% def) , blessing of light(24% light def) and char def is 60% (cleric)
MR + protection shell =70%+ 24% = 94% but capped at 75%
damage received = raw damg x(mecha bomber)x(char def)x(def buff)x(light def)x(TD) = hp reduced
damage received = 2888888 x (1-0.36) x (1-0.6) x (1-0.75) x (1-0.24) x (1-0.6) = 56 206 hp reduced
4. boss deal 1 000 000 raw damage, no any others reduction, char def 40%
damage received = 1000000 x (1-0.4) = 600000 hp reduced
5. 1 000 000 raw damage. with HOC, char def 40%, GF(max level=112 192 durable)
damage received = 1000000 x (1-0.5) x (1-0.4)- 112192 = 300000 - 112192 = 187808 hp reduced
extra note: some mobs attack come with clear buff effect. it doesn't mean def buff not work. that 1 hit of clearing buff still affect by def buff and have reduced damage.
If there is any error or anything missing and question.feel free to comment