Nin and tai pen overcomes damage reduction, if your enemy have 0 damage reduction they are useless. If you own more *ions than your enemy damage reduction every increase in them is useless. Is like stacking injury if you do not own critical.

Yes i have read what they say here, but they are wrongly, or better, superficially translated.

The correct translation should be:

Ninjutsu p3netration counters the bonus to resistance granted by damage reduction.

Taijutsu pen3tration counters the bonus to defense granted by damage reduction.

They do not reduce the effect of resistance/defense like seems they do reading the description.

They reduce the bonus effect of them granted by damage reduction.

Every 100 points of damage reduction you stack you get (very likely, hard to say how it really works, but seems that is not far from this) a boost of 1% to your resistance and defense.

Nin pen reduces this effect by 1% every 100 points stacked only for the resistance part.

Tai pen reduces this effect by 1% every 100 points stacked only for the defense part.

But the point is they do not go under 0!

So,if your ninja owns 2000 nin pen and 1500 tai pen and faces a ninja with 3000 damage reduction, then that ninja will endure hits like if he had only a 10% boost to his resistance and a 15% boost to his defense (so, if he owns 10000 res and 10000 defense, like if he had 11000 res and 11500 def).

Yes, you reduce only the additional part of them!!

But what happens if your ninja faces somebody with 500 damage reduction? Since your *ions are both higher than his damage reduction he simply gets a 0 boost to his resistance and defense (they do not go in the negatives!! ), exactly like would have happened if you had only 500 of each one p3enetration. So you would not notice any difference by adding more, nor will you notice any difference if you remove 100-200-500 of it because you are still over his damage reduction quantity.

Kakashi clones, snake, wb, ninja exams and any pve ninja have 0 damage reduction so *ions do nothing on them.

If you want to see how they impact find somebody with 2500 damage reduction and compare a long streak of results if you hit him with 2500 of both the pen with what happens if you hit him with 2000-1500-1000-500-0 and you will see how big the difference is in your average hits.

Conclusion: nin and tai *ion are good if you stack them up to 2000-2100, going over this quantity is generally counterproductive because the number of people that owns higher than 2400-2500 damage reduction are very few, while your average enemy even at high bp, owns around 1800-2200 of them.

I read this after replying before