Macro for determining Damage Reduction

[Kamira]

This is a macro which has a few customizable numbers to allow for usage on several fronts.

the macro:

Code:

/script local a,b,c,d,e = UnitArmor("player"); local x = 80; local y = 1; ChatFrame1:AddMessage(format("My armor is %i (%.2f%% DR)", b, 100*(1-y*(1-b/(85*(x+4.5*(x-59))+400)/(1+b/(85*(x+4.5*(x-59))+400))))))

when run, it'll look something like this in your main chatframe:
My armor is 30267 (66.52% DR)

now for the customization points:
local x = 80
is the target level, which means you let it stay at 80 for lvl 80 mobs, 81-82 for heroic mobs/raid trash/heroic bosses or 83 for raid bosses/non-trivial adds/non-trivial trash

local y = 1
is a coefficient for other class/gear damage reductions, just multiply all coefficients that you wish to include
i made a list of the ones i could think of, including cooldowns:

Warrior Coefficients
Defensive Stance: 0.9 (10% damage reduction)
Shield Wall (non-glyphed): 0.4 (60% damage reduction)
Shield Wall (glyphed): 0.6 (40% damage reduction)

Druid Coefficients
Protector of the Pack: 0.88 (12% damage reduction)
T10 4pc set bonus (proc): 0.88 (12% damage reduction)
Barkskin: 0.8 (20% damage reduction)

Paladin Coefficients
Divine Protection: 0.5 (50% damage reduction)
Shield of the Templar: 0.97 (3% damage reduction)
Blessing of Sanctuary: 0.97 (3% damage reduction)
Glyph of Divine Plea: 0.97 (3% damage reduction)
Improved Righteous Fury: 0.94 (6% damage reduction)

Death Knight Coefficients
Frost Presence: 0.92 (8% damage reduction)
Frost Presence (Improved): 0.9 (10% damage reduction)
Blade Barrier (proc): 0.95 (5% damage reduction)
Will of the Necropolis (proc): 0.95 (5% damage reduction)
Bone Shield (unholy, limited): 0.8 (20% damage reduction)
Icebound Fortitude: 0.5 (50% damage reduction typical for 540 defense, scales at 0.15% DR per point of defense skill, not rating)
mathy IBF: 0.7-(Defense-400)*0.0015 (30% base damage reduction, 0.15% per defense skill over 400. 0.0015 is because 1.0 = 100%, so 0.0015 = 0.15%)
Army of the Dead (Channel): 1-(dodge+parry)/100 (sum of dodge and parry chances = damage reduction)
T10 4pc set bonus (proc): 0.88 (12% damage reduction)

examples:
pally with both talents and both blessings:
local y=0.94*0.97*0.97*0.97

Frost DK with 580 defense and 50% dodge+parry popping pc T10+IBF+army while Blade Barrier is running:
local y= 0.9*0.95*(0.7-180*0.0015)*0.88*0.5

[Kamira]

as i was working on the data for this addon, i came across an addon that does very much of the same:
TankTotals: http://wow.curse.com/downloads/wow-addons/details/tank-totals.aspx

it does show other values which are mostly for numerical entertainment, but the Mitigation stat shown in the addon mimics the macro perfectly, and auto-detects what buffs, talents and other fancy things you have running, including calculating IBF DR for you

[strucktwice]

thx alot kam great job and very helpful tho i reckon youre macro needs some work or the addon you linked is also off just like the tankpoints 1

total dmg reduction from the addon you linked gives 90.+% that with the 5 times stacks from my idol
with barkskin and trinket up its 93.+% total dmg reduction

the macro you made gives me 69.93% dmg reduction that is with barkskin 5 stacks of idol and trinket
the only time its diferent is without the 5 stacks of the idol

ah hangon i c the macro only gives the dmg reduction from armor and not from my ability's

[Kamira]

if you look at total damage reduction from that addon and tankpoints, they include avoidance, i don't...

my reasoning is that avoidance isn't 100% and the interesting number is seeing what sort of reduction are you seeing from a physical attack that actually hits you

as i said about the addon: the mitigation value is the actual physical damage reduction, the DR total given by the addon is falsely labeled as it assumes that avoided attacks hit for 0 damage and accounts for average over time

i would personally rename the DR or Damage Reduction names on tanktotals and tankpoints to be named "expected damage reduction" or "effective damage reduction", as the actual damage reduction is just that, how much of an actual hit is reduced

and the numbers that we want to see in R2R applications are actual damage reduction, so we can know what sort of hits you can survive...
we don't want to know "i can survive with a 90% chance if i'm lucky with avoidance"

...
ah hangon i c the macro only gives the dmg reduction from armor and not from my ability's

the macro requires you to edit in abilities in the "local y=1" bit or they will be ignored, only the armor value (including armor gained from talents or procs) will be calculated automatically

[strucktwice]

doh.../slaps himself on the head...never realized i had to put in the numbers you posted