Reactive Interface proc question

Can someone clarify how the procs on Reactive Interface work? I have the tier 4 that gives a 75% chance of a fire DoT and a 25% chance of a damage resist debuff.

Does that mean each time I fire a power off, it rolls once and if it gets a 1-75 it DoTs and 76-00 it debuffs? Or does it roll separately for each proc?

I believe its separate for each proc, since on other interface powers, the percentages add up to more than 100%: http://paragonwiki.com/wiki/Interface_Slot_Abilities

75 times of 100 you'll get the DoT. 25 times you'll get the debuff. Sometimes neither. Sometimes both.

It's separate, so you can get both stacked. At least my Pets do when they attack. Not sure if the DoT is effected by the -Res though? Like, increases if the -Res is active. And I'm not sure if it stacks either. Like, if I were to use 3 attacks on one Target, would the DoT from each apply? Or how it works in conjunction with the Achilles' Heel Proc.

But the DoT is definitely the way to go, if anyone was wondering. It's far superior to the -Res aspect. Hell, the 75% ticks often enough if you fire off enough attacks at once, so it almost feels like 100% Chance on my Thugs/Therm Mastermind because of the amount of attacks going off at once!

- Baltoro

From my understanding that particular process works like this:

75% DoT proc hits everytime (on successful attacks) but each of the 5 ticks of damage has a 75% chance of hitting (each tick has a 75% chance at applying 13.36 fire damage; this averages to 50.1 damage per stack/attack). The single DoT stack lasts 4.3 seconds (duration of the DoT) and up to 8 of these DoT stacks can apply to a single target at the same time (while solo it is nearly impossible to saturate this without use of pets).

25% resistance debuff proc has a 25% chance of applying a 2.5% resistance debuff on successful attacks. This proc can stack up to 4 times on a single target for a max debuff of 10%.

The resistance debuff acts like a damage buff for an attack but better because it's not an additive buff, it's multiplicative and it boosts damage procs (which are not buffed by damage enhancements. I use the following formula for final damage from an attack:

Damage = [BaseDMG×(1+DMGEnhancers/100) + ProcDMG]×[1 + ResDebuff/100]

the DoT part can only stack up to 8 times, but its duration is shorter than the debuff

the DoT is the only reason i even bother with interface because all of the debuffs are essentially negligible against strong targets and not enough to bother with on weaker targets

the -tohit debuff for example is -5% per use to stack up to -20%, but if your fighting a target like AV or GM they resist that by 85-87% so the -5% becomes <-1% and your total debuff will barely be -2% even with 4 stack