Ohhh, so THAT'S how the 15% resistance works. It's incorporated into the Effectiveness vs. Effect Resistance calculation. Thanks for this!

So its still 85% chance in the end 

@all: does this still mean that for PVE, the effectiveness for a character is still best from 55 to 70? so that the diminishing return is not that high? 

or im wrong? kindly advice. 

Conclusion: Total effect resistance below 15% is equal to 0%

@SirJay 

I don't know if you have ever went on reddit or if anyone has posted about it on stove before, but it's always been suggested to not go past 55% Effectiveness for the reason posted in the OP. 56 to 70% not giving you any advantage in PvE, outside Phase 3 of Hall of Trials fights.

@Qelvah thanks! so as long as 55 is reach, then it is ok. got it!! 

This part are unnecessary and can be misleading.
"Chance of inflicting debuff = Chance of attempting debuff x (1 + Attacker's Effectiveness - Target's Effect Resistance). However, the chance of inflicting a debuff cannot exceed 85%."
If chance to attempting debuff = 50% (S1 Iseria for example)
Attacker's Effectiveness = 200% , Target's Effect Resistance = 0%
We will get Chance of inficting debuff = 0.5 x ( 1 + 2 - 0) = 75% which completely wrong.
But second part(greater detail part) was clear and perfect not sure why bother to have first part I mentioned above which just slightly shorter but not true in all case.

do i still have 100% chance to proc debuff over elemental advantage? what do they mean cannot exceed 85%

@STOVE125493060

First, the game checks to see if you even attempt to apply a debuff. You can find that chance in the skill tooltip.

If the debuff for the skill procs, then the game calculates if the target resists. That calculation is:

1 + effectiveness% - resistance%

Then choose either 85% or the result of the above calculation, whichever is lower.

If you want to achieve the maximum chance to debuff, 

resist% - .15 = effect%

A boss has 70% resist. To ensure that you're hitting the 85% hard cap, you'd need .7 - .15, or 55% effectiveness. Anything above this is wasted since there's a hard cap on your debuff chance at 85%.

As far as I can tell, there is no increased effectiveness or proc chance if you're attacking with an elemental advantage. Attacking with an elemental disadvantage gives you a 50% chance to miss your attack. On top of doing less damage, a missed attack can't proc a debuff.

Is it 85% of enemy total resistance?  If so, wyvern with 70% resist and taranor s1 would be calculated like so 75%*(1+(.85-.70)=.8625 to land debuffs.  Because at 55% effectiveness you only get 63%.  Even if you -15 from 70, you would still need 70 effectiveness to hit 85 cap? I don’t know man.

The first formula should be reworded. It's misleading. It attempts to combine both proc chance and resist chance into a single formula, but the statement following it makes no sense. It should say, "the quantity (1 + effect% - resist%) cannot exceed .85."

The way it's worded currently, with a 50% proc chance against an enemy with 70% resistance, you'd need 140% effectiveness to hit the hard cap. That is obviously incorrect.

Unless the first algorithm calculates hit chance and the second debuff chance, which is kind of redundant since the (1+E-ER) is used for both part.  Since the first algorithm includes effect chance and debuff chance. As opposed to second which calculate debuffs regardless of effect chance.  Even then it would be best to have higher effectiveness than 55% when using a skill that has 75% effect chance.

Honestly this whole system is stupid, there shouldn't be a limit on how high my chance to land a debuff if I'm stacking mountains of effectives on a unit, by that same right if I never want any debuffs to land on me I should be allowed to stack a mountain of effect res on my unit to insure that doesn't happen. There shouldn't be a 15% chance I get screwed even tho I put in the effort to build so it allows happens/never happens. 

Next thing you know your chance to crit will always be maxed at 85% chance.. Ya know, maybe that's why it feels like in this game when you're not at 100% crit it feels like it's a 50/50 chance? 

what a messy system, what is even the point of putting caps at 85%? This feels like another layer of rng. EpicRNG7 indeed.

@WeakestSoul If I'm following you correctly, you are confused about the system. Let me try and help.

There are TWO separate checks with relatively simple calculations.

FIRST CHECK: The unit's effect chance. Example: 30% chance of Stun on Spez's S2. The game checks 30% success vs. 70% fail. If success, go to step 2. If fail, stop here.

SECOND CHECK: Effectiveness vs. Effect Resistance. The calculation is [100% + (Effectiveness - Effect Resistance)]. This value has a HARD CAP of 85%.

Examples:

* Effectiveness 20% vs. Effect Resistance 50%

[100% + (20% - 50%)] = 70% chance of landing debuff.

* Effectiveness 65% vs. Effect Resistance 70%

[100% + (65% - 70%)] = 95%, HARD CAP lowers it to 85%.

Hope this helps.

And that 15% RNG will screw you over and over my friend. My ml ara 100% chance to proc with 185% effectiveness misses on dizzy with 25% chance to proc stun on me and succeed to stun my entire team  and I'm sure that dizzy doesn't even have 100 eff resistance because how can you stack effectiveness to proc 25% chance if you have 200% effect resist ? Everything in this game is pure rng because the devs don't want you to win it easily they want you to brute force everything.