If you have a Dual Wielding Sword Blader and it says +5% Defense Penetration and it shows on your stat as True Damage. Do you want to know what is the difference in these situations? or how you calculate them as damage?
If you have 20% Defense Penetration, and enemy with 6000 defense will receive your attacks as if it has 4800 defense ( 6000 * (1-0.2) ). This is usually how penetration works on most games.
For the True damage: if you have 10% true damage change. 1 out of every 10 attack will ignore the enemy defense completely. Hitting as much as your attack power and crit damage lets you.
So, having that true damage and defense penetration at the same time, whenever i bypass or ignore the targets defense, do defense penetration applied too? (TD -100% + DP -15% i.e)
I believe defense penetration reduces the defense of someone by that percentage, so let’s say they have 40% damage reduction cause of their defense, your skill that hits for 1000, will hit for 600. Now defense penetration of say 20% is gonna reduce his defense by that amount and then recalculate the damage reduction then apply your damage. True damage is simply just a % of chance your skill of 1000 is gonna hit for 1000 ignoring all damage reduction that person has. So 5% true damage means you have 5% change of bypassing all damage reduction by defense.
In short, defense penetration is percentage of additional damage you can deal depends on % of your defense penetration. And True Damage is a chance that you can bypass the defense of the target.
If you want to get any additional benefit from defense, you can buy MU Legend Zen on U4GM.com, and you can also read some useful guides on defense. Hope it can help you improve your defensive ability and have true damage at the same time.