(why are you comparing MoS to gladiator helm by itself? what happened to 30+str title, corundum delusion comparisons?)
I'm not comparing it to the helmet itself. "I said MoS adds 16, while Gladiator (+Helmet) adds +13." The title adds +12, while the Gladiator Helmet adds +1 over Delusional Cap, thus making it +13. Likewise, the Cap isn't part of the +16 that comes with MoS. I simply removed the constants.
The 404 max dmg does not appear in character screen. Does the MoS title show increases of 16 when the combined dual wield range is around 300, leading you to believe that it will use 404 as the variable? Otherwise the real max you're receiving without str would be 10, not 16. In which case, gladiator gives higher increase in damage.
I imagine each sword-hand max is multiplied with the MoS dmg increase % and combined for the character screen dmg range, unless the 16 max dmg you refer to is tacked onto the variable max used in actual calculations of dmg rather than displayed in the face value. If this is the case, then MoS is useful before a character hits the screen value of 300 max dmg.
I don't have MoS title, but I used logic to do the calculations. You said that you image "each sword-hand max is multiplied with MoS damage increase", which is exactly what I did. Again, I just simplified it for the sake of calculations.
MoS increases your overall damage by 4%. Whether you combine the numbers and add 4% (what I did) or add 4% then combine the numbers (what you said) the end result is still 4%.