Hello. I've been trying to wrap my head around damage reduction (DR) in D3 for a while now, and thought I'd put pencil to paper to help solidify some of my ideas about it. This post is just a dump of what I came up with in Excel based on what is known about DR at the moment.
I used monster level 63 for all formulas, but it's worth noting that changes in monster level are relatively insignificant in the data. If you're just starting Inferno, your numbers will be almost identical.
Comparing Armor and Resistance
This first chart shows how increasing your armor or resistance impacts DR of the respective type.
Increasing DR
How much armor does it take to increase your DR by 1%? The answer to this question changes depending on your current armor/resistance value, so this chart shows about how much more armor or resistance is needed given your character's current value.
Overall DR
Overall DR is calculated by combining all of the specific DR types into something like a weighted average. Due to the co-dependence of the variables, there's no way to say how much a given amount of, say, armor will impact your Overall DR without also considering the amount of other specific DR types you have. This first chart therefore looks at how armor impacts your Overall DR for given amounts of resistance. ("Melee" here refers to the DR bonus for monks and barbarians.)
Then we have a similar chart showing how resistances impact your Overall DR for given armor values.
I've attached the raw Excel file for anyone who cares to play around with it. Let me know if you see any problems!
Edit: there were problems! Thanks to the commenters. I had the scale off by a factor of 10, so these charts should be a fairer comparison of armor and resistance. I've also updated the attached Excel file as of 5-24.
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I'll update the graphs ASAP.
Edit: hopefully they look better now. Thank you!
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All of the formulas for the data presented here came from Click to Loot's Diablo III Combat Mechanics Compendium, though I have seen the same formulas in other places as well. If you haven't read their section on damage reduction, you should do that before continuing.
I used monster level 63 for all formulas, but it's worth noting that changes in monster level are relatively insignificant in the data. If you're just starting Inferno, your numbers will be almost identical.
Comparing Armor and Resistance
This first chart shows how increasing your armor or resistance impacts DR of the respective type.
Increasing DR
How much armor does it take to increase your DR by 1%? The answer to this question changes depending on your current armor/resistance value, so this chart shows about how much more armor or resistance is needed given your character's current value.
Overall DR
Overall DR is calculated by combining all of the specific DR types into something like a weighted average. Due to the co-dependence of the variables, there's no way to say how much a given amount of, say, armor will impact your Overall DR without also considering the amount of other specific DR types you have. This first chart therefore looks at how armor impacts your Overall DR for given amounts of resistance. ("Melee" here refers to the DR bonus for monks and barbarians.)
Then we have a similar chart showing how resistances impact your Overall DR for given armor values.
I've attached the raw Excel file for anyone who cares to play around with it. Let me know if you see any problems!
Edit: there were problems! Thanks to the commenters. I had the scale off by a factor of 10, so these charts should be a fairer comparison of armor and resistance. I've also updated the attached Excel file as of 5-24.