What situations are you testing it in?

18k pen self-sourced is going to be significantly over cap against enemies with 9.1k resists (most of overland) or in PvE situations where Major and Minor Breach are applied (so basically all of them, if you have a tank with Pierce Armor or a necro with graveyard or someone with Ele Sus/Drain). Adding more pen won’t do any more damage in those circumstances.

jtm1018 wrote: »

What is the highest penetration allowed ingame? Is there a pen cap? Pve and pve?

There is no hard limit on the amount of pen, but it is limited in effectiveness by the armor of your target.

Mobs as a general rule have either 9.1k or 18.2k resists. Dungeon and trial enemies have 18.2k, regardless of difficulty. A few years back, testing showed that Maelstrom had a mix of 9.1, 18.2, and some mobs were in between. I’m not sure if that was ever standardized.

In group settings, you can generally count on at least Major and Minor Breach, and often an infused crusher enchant applied to the boss by a support. A support dps might run Alkosh or a tank might run Crimson Oath’s Rive. These armor debuffs and your personal penetration combine towards the limit of the target’s armor. So if a boss has 18.2k armor but is debuffed with Major and Minor Breach and an infused crusher enchant, you have only 7170 armor left to get through. If you have 18k pen on your own in that situation (through CP, traits, light armor, sets, etc.), 10,830 of it is wasted.

Players can stack resists much higher. They are only effective up to 33,000 (at CP 160+), which represents 50% less damage taken. You can continue to stack them above that if you would like to give yourself a buffer in the event that players apply debuffs to you in PvP. For example, if you start at 33,000 and get Major Breach put on you, you are at 27,052. But if you start at 39,000, then only 33k counts, but getting hit with Major Breach from someone still allows you to stay at armor cap.

I don't think this set would be all bad in a No-CP campaign?