actual effects of defense reduction

0. before starting
defense(%) = defense / (attacker level x 200 + defense)
in case of direzie(not illusion), if the phys damage reduction is 89%, then defense stat is about 113272
fire turtle boticelli is about 84.9%, so about 78505
and when we calculate in this thread, we count out piercing

1. cutting fixed amounts
defense - debuff amount = applied defense
example : bremen lv20, ex passive lv4( phys def -9458)
boticelli : 78505 - 9458 = 69047(83.1%)
84.9% -> 83.1% , so your damage done to him increases by 11.9% more than before
direzie : 113272 - 9458 = 103814(88.1%)
89.2% -> 88.1% , so your damage done to him increases by 8.1% more than before

stuff that apply to this : wm awakening passive, bremen, rhasa, shururu, acid, m nen awakening passive, tortoise, ex tortoise, nail of pain, etc

ps. even if the target's defense is normally low, it does not get debuffed beyond a certain point.
some skills have reduced effects against named/champion/boss mobs(rhasa, tortoise)

2. cutting in percentage
defense x (1.00 - debuff amount) = applied defense
example : enchanted full swing(25%?)
boticelli : 78505 x 0.75 = 58879(80.8%)
84.9% -> 80.8% , so your damage done to him increases by 27.2% more than before
direzie : 113272 x 0.75 = 84594(85.9%)
89% -> 85.9% , so your damage increases by 28.2% more than before

stuff that apply to this : enchanted full swing, flu's seal,...anything else?

ps. the two mentioned above stack with each other
enchanted full swing of same elements dont stack

3. conclusion
with fixed debuff amounts, the greater the defense, the lesser the effect
if the target's defense is immense, as in lv70 outerverse, the effects is quite small(although better than nothing)
with percent debuff amounts, the greater the defense, the greater the effect
but the difference is quite small with each other(27.2% more and 28.2% more...1%...lol)

4. bonus
some foes, such as beat busty, defense buff direzie, and the green hell demon in the spacial lv70 outerverse map, no matter the debuff, it wont matter(0.01% damage and 0.15% damage is that and that)