[AlexanderHowl]

Armor Divisor and Hardened are both enhancements though while Damage Reduction is an advantage, so you are comparing apples to oranges. Now, I could see make Damage Reduction into an enhancement for DR, with Damage Multiplier being an enhancement for Innate Attacks.

In that case, Damage Reduction would be a 50% enhancement for DR, with injury divided by (DR/10, minimum 1), with Armor Divisor having no impact on Damage Reduction. Damage Multiplier would be a 100% enhancement for Innate Attack, with injury multiplied by (Innate Attack Level/10, minimum 1), with Hardened having no impact on Damage Multiplier. In that case, a character with DR 20 could have Damage Reduction /2, DR 30 could have Damage Reduction /3, DR 40 could have Damage Reduction /4, etc.