So, after a couple of discussions both in game and in other sections on jsp I figured it's time to make this clear once and for all. A lot of people seem to believe that resistances and armor gets less effective the more you have, that at some point its not worth getting more due to how much you need to mass up even 1% reduction in your character sheet. While your sheet doesn't outright lie, it appears its misleading enough to give a lot of people the wrong idea about how armor and resistances work. The purpose of this post is to educate you in game mechanics and hopefully give you some helpful advice even if you were already familiar with them.
I play all classes, although my focus atm is mostly on barb (hc) and wiz (sc). Since we're dealing with very basic game mechanics I think this information is useful to anyone though.


So you're telling me I got it all wrong?

The misconception is, as mentioned, that armor and resistances are suffering from diminishing returns. IE, that one point would at some point be worth less than it was at a previous point. For example, the 100th point of resistance or armor would be worth less than the first point. This is wrong. Armor and resistances increase your survivability linearily. This is apparently counter intuitive to some, as the character sheet shows a decreasing percentage of reduction gained per point of resistance/armor the more you have, but I'll explain exactly why it is so.

So how does it work then?

To understand this you will need the formulas the game use to calculate reduction from resistances and armor:
Damage Reduction from resistance = Resistance / (Resistance + (5 * mLvl))
Damage Reduction from armor = Armor / (Armor + (50 * mLvl))
In these formulas mLvl is the lvl of the attacking monster.

What you'll see is that the benefit from armor and resistance in terms of percentage shown in character sheet is indeed diminishing, but those numbers appear to be hard to interpret to some. To understand fully we need to introduce another term, effective hp, EHP.
Your EHP is basically the amount of incoming damage prior to any mitigation that your character can sustain before dropping dead. If you have 10.000 hp and a total of 0% reduction your effective hp is 10.000. If you have a total reduction of 50% you can suddenly take 20.000 damage before you die; your EHP is 20.000 with 50% reduction.

For example. a character with 300 resistances will have 50% reduction vs lvl 60 mobs according to the formula above. With 10.000 hp your EHP will thus be 20.000.
With 600 resistances you have 66.6666% reduction vs lvl 60 mobs which lets you take 30.000 damage before death. See how the extra 300 resistances "only" increased your percentage of reduction by 16.66%, but at the same time your effective hp went up by just as much as the first 300. The actual value of the extra resistances didn't diminish at all, even if the character sheet may have fooled you into believing so. Exactly the same thing goes for armor.

Oh, wow, so, what now?

Well, first of all, this helps you look at gear upgrades in terms of survivability for what they actually are. You don't have to be fooled by the tooltip saying its only a 0.5% increase in reduction believing thats not gonna do much at all for you. If you're already at 90% that 0.5% is actually a huge increase in effective hp.

There's also a few "hidden" perks to increasing the amount of damage you mitigate over just inflating your hp. For example, if your build relies heavily on heals that are not based on a percentage of your life, they will actually be much more efficient with high DR and low hp at the same EHP values as the opposite; high hp and low DR. Heals based on a % of your life (like revenge) are actually completely unaffected. The only thing that matters for those is effective hp.

The same goes for items with the increases life by x% mods. They don't need high vita to be good. They will increase your EHP by the same % nomatter what your hp is.

I might come back to this post and fill in the blanks if there are any, til then, hope I helped you understand the game a bit better.

This post was edited by Blodulf on Jul 29 2012 04:16pm

Never thought of it that way, thanks.

edit: good guide but how does the ehp scale with an ilvl 63 monster? I'm stuck on the ehp calculation (no ezmode formula given)


i've got 48.78% dmg reduction @ 300 resist and 65.57% dmg reduction @ 600 resist...

This post was edited by boognis on Jul 29 2012 04:45pm

Nice analysis! To summarize, you conclude that effective HP scales up linearly with damage reduction, with effective HP being a reliable measure of survivability.

However, the reductions themselves are in fact affected by diminishing returns.

Yep, I'm assuming the mlvl 60. In inferno mlvl is only decided by act.
Act 1: mLvl 61
Act 2: mLvl 62
Act 3-4 mLvl 63

Truth is the impact of mobs being 3 lvls higher doesn't do *that* much to your reductions. Example:
Barb 40k hp
10k armor 800 all res (rounding numbers with 2 decimals, EHP by even 100's)
vs 60: 76,92% armor DR, 72,73% res DR = 635500 EHP
vs 61: 76,63% armor DR, 72,40% res DR = 620100 EHP
vs 62: 76,34% armor DR, 72,07% res DR = 605300 EHP
vs 63: 76,05% armor DR, 71,75% res DR = 591200 EHP

Conclusion: The reason act 4 mobs oneshot people isnt the diminished effect of armor and res with increased attacker lvl. The reason act 1 mobs barely dent your hp and those opressors gib you in 2 hits is simply because they're doing *that* much more dmg.

No, you're mistaken. Someone gave me a good example earlier today. Thats like saying weightgain has diminishing returns.
Weigh 100kg put on 10kg = 10%
Weigh 200kg put on 10kg = 5%
Seemed clear at the time anyway

What we need to look at is what res and armor actually does for us, not what the character sheet tells us, anyway.

Could make an excel sheet for it but I hate excel, the purpose was just to open peoples eyes to how it works, not give them a supertool

However.. just remembered this site: http://rubensayshi.github.com/d3-ehp-calculator/

Very helpful.

This post was edited by Blodulf on Jul 29 2012 04:49pm

Stay in school, kids

Tl;dr/basically:

With 50k life and no all resists or dodge and the mob hits for 50k:

When you have 0 armor, it takes 1 hit to kill you.
When you have 3100 armor, it takes 2 hits to kill you.
When you have 6200 armor, it takes 3 hits to kill you.
When you have 9300 armor, it takes 4 hits to kill you.
When you have 12400 armor, it takes 5 hits to kill you.

This post was edited by jf59 on Jul 29 2012 05:39pm

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