New features under Update 12: Attack Mod and Damage Mod are both set to max of either dexterity bonus or strength bonus. 10% Armor-Piercing allows players to ignore 10% of a targets fortification. Example: Monster A has a fortification of 100%, on confirmed critical hits only On Crit type effects (Burst for instance) would go off and the base weapon damage would not be multiplied. With 10% Armor-Piercing, 10% of those confirmed critical hits would ignore the fortification and score a regular critical hit (with base weapon damage multiplied). Similar for Sneak Attack damage.
From DDOcast Ask the Devs 9;
Jerry: “Rogues get their subtle backstabbing enhancement, where level one gives you 10% hate reduction, level two is 20% and level three is 30% hate reduction. Treason, the named short sword form the Stormreaver has an ability which is 20% hate reduction. My question is a two-parter: 1. Does Treason stack with subtle backstabbing, so if I have two levels of subtle backstabbing and wielding Treason will I have a 40% hate reduction?”
MadFloyd: Actually it does stack but you have something like a 36% hate reduction, so you would have 20% for the subtle backstabbing and you’d get 20% for treason, but they’re not purely additive so basically it’s sort of like 80% times 80% so you sort of get like 64% as a result.
Jerry: Oh ok, so it would essentially stack on top of that other 20%
MadFloyd: that’s correct.
Jerry: Question 2 here: Does the treason effect affect weapons in your offhand – so wielding treason in my main hand and welding a +2 dagger in my offhand would my offhand gain the benefit of the treason’s 20% hate reduction?
MadFloyd: Yes, it would because basically what that does is reduce threat generated by any melee damage, and that would include whatever your offhand is doing as well.