You'll need 5850 additional Penetration with all debuffs (Alkosh + Torug's Crusher + Fracture/Breach) in the context of Trials.
All stam CP unless noted before the image is Dual Wield/Bow CP! As requested, the CP allocations have been re-adjusted from recommended maximum penetration value to the lowest possible in order for people to "dial up" penetration easily.
Mundus Stone: Shadow on all DD classes.
Weapon Traits for Harrowstorm DLC
Precise Frontbar, Infused Backbar (Magicka)
Nirnhoned/Infused Frontbar, Infused Backbar (Magicka Necromancer)
Sharpened Frontbar, Infused Backbar (Stamina, 2 Hander)
Precise Frontbar, Infused Backbar (Stamina Necromancer, 2 Hander)
Sharpened/Nirnhoned Frontbar, Infused Backbar (Stamina, Dual Wield)
Precise/Nirnhoned Frontbar, Infused Backbar (Stamina Necromancer, Dual Wield)
Stamina Necromancer (2 Hander): 56 Master-at-Arms 44 Thaumaturge 56 Precise Strikes 58 Piercing 56 Mighty
Stamina Sorcerer (2 Hander): 72 Master-at-Arms 40 Thaumaturge 66 Precise Strikes 36 Piercing 56 Mighty
Adjust the Spell Erosion and Piercing below as you see fit for your 4-man/raid groups.
Red/Green CP Allocations (for ALL Trials/Arenas) along with MK/Zen, Healer, Tank/Tank Tactician CP are located here:
https://www.nefasqs.com/knowledge
and available on Discord:
https://discord.gg/p8p7wn9
Both sources are copy/paste-able!
Keep in mind while all of the CP allocations do work effectively and have gotten top results (TTT, GH, IR, Unchained, Godslayer, scores, etc), always see if you need to readjust the given allocations/templates for your own groups and your own needs!
BIG THANKS to: t3hasiangod, atsona, natsu, Mapurr, Stileanima, skinnycheeks, LIKO, lulu, Timewizard, slaymane & other professors from Atsona's Academy!