Repository of Essential EQ Mechanics Knowledge

there is a ton of info all over various EQ sites - some of it is kind of easy to find, some of it is buried deep in multi-page threads.
while tactics and opinions on how best to approach certain situations will always be fluid and somewhat subjective, there are certain basic facts about how EQ works which are not obvious, but which can greatly enhance a person's understanding of how the game operates.
this thread is intended to be a one-stop repository for that critical game mechanics information, which so many of us take for granted but others may not even be aware of.
(this is meant to be a companion to my other thread detailing knight raid strategies which also included a bunch of info about how hate works:
https://forums.station.sony.com/eq/...o-tanking-info-dump-for-the-commonwealth.180/)

when determining whether or not you are hit by an NPC, EQ goes through the calculation in this order:
Block, Riposte, Parry, Dodge, Shield Block, Miss
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every mob has 20 possible values it can hit you for - every single mob in the game has a 20 point damage spread, without exception.
this spread is determined by this formula: DB+DI*(1-20)
DB = damage bonus. a static number assigned to every mob. this number is reduced by the Shielding stat on gear.
DI = damage interval. a static number assigned to every mob. this is multiplied by (1-20) based on the mob's atk vs. your AC.

so, if we pretend that a mob has a DB of 10 and a DI of 10, you get the following:
10+10*(1-20)
min hit: 10+10*1 = 20
max hit: 10+10+20 = 210

if you assume 35% shielding you get:
min hit: 7.5+10*1 = 17.5
max hit: 7.5+10*20 = 207.5

warriors get a 5% reduction to DI inherent to the class (with higher innate reduction possible via AA, though the AA bonus reduction does not stack with Defensive) from whatever the final number (which basically translates to -1 DI, but not to drop under DI*1), and Defensive Disc and its variants give a 45% reduction to DI from whatever the final number is - meaning that a warrior in defensive is reducing the DI by half.

now, in EQ when you take all these factors, your AC vs. the mob's atk creates what's called your DI distribution - this is basically what percent of hits are where in the possible range of DI.
more AC = more hits will be lower in the DI spread.

here is how you can think of this visually:


in this graph, the player's AC destroys the mob's ATK and most hits are on the lowest possible end of the DI distribution.
that right there is what AC does for you. it makes more and more of the hits be on the low end of the spectrum.

now, since every mob has a different ATK value, and your DI distribution is always about mob ATK vs. your AC, that graph will look different for every mob that you ever tank.
but, it's a good idea for every tank to periodically pull up gamparse and load the Tanking tab for a given mob that you tank, and look at your DI distribution.

if you're interested in figuring it out... if you take the smallest difference between two regular hits (or use gamparse to graph it out like above) - that difference is the mob's DI.
(note that in most parses this is going be a little messy due to things like runes and vie and such changing your damage spread, in order to get it nailed down for certain you need to get 20 different hits without any sort of absorption - but even then, you can more or less figure it out)
for example, in the above chart, we learn that Daosheen has a DI of 199 (it's 199 point of damage difference between each hit)
if you take the lowest hit and subtract the DI, 1338 - 199 = 1139, which is Daosheen's DB.
so to figure out how much damage daosheen can do, using the damage formula, is:
1139+199*(1-20)
min hit: 1139+199*1 = 1338
1139+199*18 = 4721 (18 is the highest number on the char listed, and the there is an 8 point difference in the calculation here probably due to vie screwing up the damage numbers, but the math is still right)
max hit: 1139+199*20 = 5119
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AC works by reducing the value of random (1-20) roll of the NPC damage formula.
(note that whenever AC is discussed, it must be remembered that in EQ, we the players do not know the exact formula for how AC works - we know what it does, and roughly how it does it, but there is no known formula which easily breaks NPC damage down to "X AC against Y atk reduces DI by Z", so much of the discussion about AC is conceptual terms, even though some values are known explicitly.)
the exact effect AC has on the value is highly variable and evidence suggests that in all instances it is a scaling value that is largely impacted by Diminishing Returns (ie, it hits a point where adding more AC has less and less of an effect).
the diminishing returns of AC are seen in-game in two different but important ways:
1. the AC softcap
2. DI reduction scaling

1. AC Softcap:
simply put this a value at which point adding more AC (via gear or buffs) no longer provides the full benefit listed on the item/buff.

2. DI reduction scaling:
this is kind of hard to describe simply in text...
basically the way combat and damage in EQ works is that the (1-20) DI portion of the formula is scaled in such a way that it's very nearly impossible to ever reach a point where you overcome every roll and get a DI1 on every hit.
even if you were to let a level 1 fire beetle hit you, it will still get some variance in its damage output, meaning it is getting something higher than 1 in its DI rolls.
the easiest way to express this is: there comes a point where your AC is high enough against certain mobs that adding more AC effectively does nothing against that mob.
(this behavior leads to one of two conclusions in terms of thinking about how EQ's damage formula most work:
1. AC effects the DI roll by a %, and as you get lower in the DI range % shifts become so small they effectively stop doing anything.
2. there is an absolute amount that AC can reduce the DI to, and once every hit is being reduced to that point the damage is just a random roll on the remaining available numbers.
(for example, if 3 is the lowest DI your AC can ever reduce a hit to, then damage is a random 1-3 DI, because you can never reduce that)
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AC number values - in-game display, rAC, and the softcap.
first and foremost, the thing most people don't seem to realize about AC is that the number listed in-game is 100% absolutely meaningless.
i'll say that again: your AC value in EQ is rubbish and is not in any way related to any actual calculation.
in in-game display of AC does not calculate the softcap on items/buffs/AAs, does not stop adding AC from agility past the hard cap, and adds AC to the display number based on your Avoidance mod2.
the more AC you have the higher that number will be in game, true, but that value in EQ is nothing but a "MOAR!!" number that doesn't translate into any kind of useful information.

your 'real AC' (or rAC) is derived thusly:
take your total 'true' AC (which is the AC on all your slots added together - or, if using magelo, the AC tab under Modifiers), subtract the amount of pre-softcap AC for your character, multiply the remainder by your softcap returns, then add that to you pre-softcap AC.

let's use my toon as an example. in magelo, my AC tab is 4000 AC.
assume that at level 90 the shadowknight AC softcap is probably somewhere around 750 (not positive on this, if anyone has the numbers let me know and i'll update this), and my shield has 281 AC - and if you didn't know, the AC from your shield is always 'pre softcap', so that gives us 750+281 = 1031 AC that 'pre' softcap.
with max AAs giving 55% bonus softcap (see below) that makes my softcap about 1598.
4000 - 1598 = 2402. so, i have 2402 AC subject to the softcap.
SK softcap is now about 40% (again, correct my numbers and i'll update this post). 40% of 2402 is 1442.
so, 1598+1442 = 3040ac. so, 3040 is my rAC just from gear.
(if you add up all the AC from all your buffs and then take 40% of that number and add it on top, that's your rAC with buffs)

Combat Stability increases your AC softcap:
Combat Stability Values -
AFFECTNAME BASE_EFFECT_1
1 - ACLimitMod 2
2 - ACLimitMod 5
3 - ACLimitMod 10
4 - ACLimitMod 13
5 - ACLimitMod 16
6 - ACLimitMod 19
7 - ACLimitMod 22
8 - ACLimitMod 25
9 - ACLimitMod 27
10 - ACLimitMod 29
11 - ACLimitMod 31
12 - ACLimitMod 33
13 - ACLimitMod 35
14 - ACLimitMod 37
15 - ACLimitMod 39
16 - ACLimitMod 41
17 - ACLimitMod 43
18 - ACLimitMod 45
19 onwards is 1 per rank
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Combat Agility works by increasing your chance to be 'missed' by an NPC - in conjunction with the Avoidance mod2, this is checked against NPC Accuracy to determine whether you are 'hit' or 'missed'.
Combat Agility AA line has the following values:
Combat Agility Values -
AFFECTNAME BASE_EFFECT_1
1- Evasion 2
2 - Evasion 5
3 - Evasion 10
4 - Evasion 13
5 - Evasion 16
6 - Evasion 19
7 - Evasion 22
8 - Evasion 25
9 - Evasion 26
10 - Evasion 27
11 - Evasion 28
12 - Evasion 30
13 - Evasion 32
14 - Evasion 33
15 - Evasion 34
16 - Evasion 35
17 - Evasion 37
18 - Evasion 39
19 onwards is 1 per rank
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when you FD, an NPC keeps you on its hate list until it returns to its 'home' point, at which point it will wipe its hate list after a few seconds.
the 'home' point for NPCs is their spawn location - which for roamers means the spot along their path where they actually pop into the world.
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Awesome post.

little math fail there though

gah, you're right should be 6.5 not 7.5!
well it's too late to edit that post now unfortunately - but the general idea of it still stands.

I thought the hit check order was Riposte, Block, Parry, Dodge, Shield block, Hit/Miss. I'll parse my monk on a ripo disc tonight and follow up. If there are any blocks in the parse then I'll actually be disappointed. This would mean the potential dps is reduced during a swarm.

if that order is wrong, please do post here to correct it - this is all old info gathered from several class sites over the last decade, so if some of it is no longer correct and/or my brain has decided to up and hallucinate something which isn't accurate, by all means please say something.

The hit order is indeed Riposte, Block, Parry, Dodge, Shield block, Hit/Miss. On ripo disc there were no blocks, parrys, or dodges.

well i'll be damned - i honestly think that either they changed that at some point, or else there has been the addition of some kind of riposte mod to the game in recent years that changed it.
well, sadly i can't edit the post now, but if a mod ever catches this and would like to edit it for me it would be much appreciated.

heroic characters = more new tanks = this info could be useful for people, so bumping this thread.

posting this so it's never lost:

https://forums.station.sony.com/eq/index.php?threads/ac-vs-acv2.210028/

Nice post but isn't this the sort of thing that belongs on the new wiki?

Can we dive into how Heroic Stats such as Hdex and Hagi effects these parse values? Correct me if I'm wrong that for every 25 Hagi = 1% dodge and for every 25 Hdex = 0.8% reposte/parry. I often see the argument that at higher ends you should sacrifice 10-15 ac on an aug that has 5-8 Hagi/Hdex. Especially if it puts you over the next interval of 25.

That's a damn good idea.

Just quoting you so you get the notification. This info (with your corrections since you can't edit here) would be great for the wiki.