tl; dr >> mace over axe and sword at max. CJ.
As you already implied. Defense Penetration is better whenever the assumed enemies’ defense increase is higher than your assumed attack increase.
By way of illustration:
you creatures has
- 22% from Sword
= 1222 Attack
- 30 % due to Defense Penetration from Mace
= 2100 Defense
So we have got:
1222 attack against 3000 defense, difference = 1778
1000 attack against 2100 defense, difference = 1100
I do not know how the damage calculation works but 3000 against 2100 is quite a number.
You are going to take on max CJ so the enemies defense is much higher than your attack stat. Please also take into consideration that defense penetration also affect spells.
Axe’s attack damage increase is a different case, though. Here is the question how much initial damage do you dish out with attacks.
I. e. 10 000 initial + 30% from Axe = 13 000 hmmmm does that really help?
At the best get for your attackers an artifact with innate attack damage, attack stat and defense penetration and for your spell casters one with spell damage, int and defense penetration.
I think a mace is you best choice since you get guaranteed 30% and at max CJ the penetration is dependent on the impressive high stats of the enemy not on yours.
If you die after one attack anyways because of max CJ then also go for Start battle with berserk.
I would love to see your max CJ build - the whole community is waiting for a working team
Best luck to you and your creatures