I decided to check out the numbers myself. Using Valks damage calculator, assume all other variables are constant (weapon damage, potency, etc). I will only change the Strength attribute.

STR | Avg Weaponskill Damage | Avg Autoattack Damage
500 | 138.612 | 124.485

-10% STR from RoH 500*.1 = 50 so 500-50 = 450

450 | 126.037 | 113.107

126.037 / 138.612 = 0.909 ~ 91% which is about 9% damage reduction

113.107 / 124.485 = 0.908 ~ 91% which is about 9% damage reduction

600 STR:

600 | 163.762 | 147.241

-10% : 600*.1 = 60 so 600-60 = 540

540 | 148.672 | 133.587

148.672 / 163.762 = 0.907 ~ 91% again about 9% damage reduction

133.587 / 147.241 = 0.907 ~ 91% again about 9% damage reduction


I know this isn't a lot of data or trials, but for the most part it seems that RoH's STR reduction is a close damage reduction to Storm Path's 10%. That's probably why it seems negligible.