D&D 5E Trading AC for DR in 5e

[I'm A Banana]

So lets say I had a player who liked the idea of armor giving old-school DR. "Old school" because damage resistance in 5e is a half-damage binary state, rather than "subtract a bit off of every instance of damage."

She's aware of all the problems with using DR instead of AC (like, how it increases the fiddly math in the game to subtract a few HPs off of every attack rather than have a binary hit/miss system). She is fine with this. She wants armor to absorb damage, not make you harder to hit.

I'm not interested in changing the table rules for everyone - most of the players are fine with armor giving AC. This one prefers the fiddly bits, and I'd like to indulge her.

In 5e, how much DR should a point of AC be worth?

Let me know your thoughts!

 

[Fanaelialae]

So lets say I had a player who liked the idea of armor giving old-school DR. "Old school" because damage resistance in 5e is a half-damage binary state, rather than "subtract a bit off of every instance of damage."

She's aware of all the problems with using DR instead of AC (like, how it increases the fiddly math in the game to subtract a few HPs off of every attack rather than have a binary hit/miss system). She is fine with this. She wants armor to absorb damage, not make you harder to hit.

I'm not interested in changing the table rules for everyone - most of the players are fine with armor giving AC. This one prefers the fiddly bits, and I'd like to indulge her.

In 5e, how much DR should a point of AC be worth?

Let me know your thoughts!

It will vary depending on the creature she's facing. If she's facing a creature that deals 3d8 + 5, one point of AC will be worth much more DR than if she's facing a creature that deals 1d4 + 3 damage.

My best suggestion would be to convert her AC into some percentage of damage reduction. So, just for the purposes of illustration, maybe Hide Armor reduces incoming damage by 15% while Chain Mail reduces it by 30%. I have no idea whether 1 AC = 5% DR would actually work though.

 

[Warbringer]

Tough question.

I've just used a hit point pool, where the poolis 5 HPs per AC as written, then reduced the actual AC of armor by 50%.

Player can reduce the attack by upto 50% of the attack. When armor has no hit points reduce its AC by 1 until then.(mend has no effect)

When attacked by a creature 1 size bigger, max is 25% per hit, 2+ sizes, you can't use your hp pool. Large and tower shields grant the defender an effective bonus to size for this purpose.

 

[Sunseeker]

Different types of armor would provide different levels of DR. I'm assuming her base AC is 10? I'm not sure what class she'll be running, but lets be honest here: almost everything can hit an AC of 10, it's lower than the armor of a Skeleton, Bandit or even a Kobold (11). I would probably be generous with her and give her every point of armor-based AC above 10 as damage reduction. This would be potentially very powerful for a tank-type character, at least at lower levels. Once things start hitting for +8 v ac, giving them essentially a 50/50 chance to hit the character, it will be much less powerful. However, if the character was wearing anything less than full plate and a shield, I think it would work out to be reasonably balanced.

 

[Dausuul]

Okay, after revising my calculations a bit...

Based on what I consider reasonable assumptions (enemy has +8 to hit for 1d8+5, defender has base AC of 11 thanks to Dexterity or other factors), I get roughly 0.6 DR per point of AC. I would calculate the benefits of armor based on that, and then adjust to the nearest half-point.

Padded or leather armor (+1 AC): Round damage down to even numbers. (If you get hit for 9 points of damage, you take 8. If you get hit for 8 points of damage, you still take 8.)
Studded leather or hide armor (+2 AC): DR 1.
Chain shirt (+3 AC): DR 2.
Scale mail, breastplate, ring mail (+4 AC): DR 2, and round damage down to even numbers.
Half plate (+5 AC): DR 3.
Chain mail (+6 AC): DR 3, and round damage down to even numbers.
Splint armor (+7 AC): DR 4.
Plate armor (+8 AC): DR 5.

Note that this will make the character essentially invulnerable to weak enemies like goblins, but vulnerable to hard-hitting foes like giants. You may wish to adjust the baseline if one type of enemy is more common.

I would also remove the DR 3 from the Heavy Armor Master feat, and replace it with +5 AC (against nonmagical slashing, bludgeoning, and piercing attacks only); your skill allows you to use your armor to deflect attacks. Thus, a character in plate armor using these rules would have AC 15 and DR 5, instead of AC 18 and DR 3.

 

[Jeff Albertson]

Just use the d20 SRD/Unearthed Arcana variant.

 

[Fanaelialae]

I did some back of the envelope calculations and it looks like 5% DR per point of AC (over 10) is correct. So Plate Armor should grant 40% DR (against all attacks, but not saving throw based effects).

As [MENTION=58197]Dausuul[/MENTION] correctly points out above, using a flat DR number is going to make her basically invulnerable to weak threats and very vulnerable to powerful threats. That's why I think you should go with a percentage based DR instead. It will keep weak creatures relevant while preventing dangerous creatures from rolling over her.

Also keep in mind that this means that she will be subject to many more "on-hit" effects than other PCs with the same armor. In a fight with wolves, for example, she's likely to be subjected to many more Strength saving throws (to avoid being knocked prone) than a similarly armored ally. If she fights Giant Crabs or a Roc, chances are she's going to be grappled, which might not be the same foregone conclusion for her companions. In essence, things are likely to feel significantly different for her.

EDIT: On the plus side, it would mean she'd be a little less susceptible to crits than her companions, since natural 20s ignore AC but DR still applies.

 

[Dausuul]

As @Dausuul correctly points out above, using a flat DR number is going to make her basically invulnerable to weak threats and very vulnerable to powerful threats. That's why I think you should go with a percentage based DR instead. It will keep weak creatures relevant while preventing dangerous creatures from rolling over her.

In principle, this is a reasonable argument, but in practice that's way too much calculation IMO. Even a flat DR adds noticeably to the amount of time it takes to "process" damage. Applying a percentage modifier would require busting out a calculator for each and every hit.

I don't think it's necessarily a bad thing that DR makes you tougher against weenies and weaker against giants. It's a tradeoff. Sometimes you come out ahead, sometimes behind; just try to find the correct balance point for your table.

Also keep in mind that this means that she will be subject to many more "on-hit" effects than other PCs with the same armor. In a fight with wolves, for example, she's likely to be subjected to many more Strength saving throws (to avoid being knocked prone) than a similarly armored ally. If she fights Giant Crabs or a Roc, chances are she's going to be grappled, which might not be the same foregone conclusion for her companions. In essence, things are likely to feel significantly different for her.

This is a very good point. It might be worth allowing the character to apply her DR as a bonus on saving throws against "on-hit" effects. Or simply rule that a hit whose damage is reduced to zero can't trigger effects.

 

[Jester David]

I wonder if it would work to replace the DR with a "soak die" where you roll and ignore a certain amount of damage. So, on average, it's the same but sometimes you'll take more and sometimes you'll take less.

 

[Fanaelialae]

In principle, this is a reasonable argument, but in practice that's way too much calculation IMO. Even a flat DR adds noticeably to the amount of time it takes to "process" damage. Applying a percentage modifier would require busting out a calculator for each and every hit.

I don't think it's necessarily a bad thing that DR makes you tougher against weenies and weaker against giants. It's a tradeoff. Sometimes you come out ahead, sometimes behind; just try to find the correct balance point for your table.

In fairness, you can make the calculation easier by going the old Thac0 method and reversing the math (if you have DR 40%, multiply the damage by 60% to get how much you take).

Another thing to keep in mind with flat DR is that she will be stronger against a creature with many attacks (Marilith) and weaker against creatures with a single, powerful attack (Triceratops).

This is a very good point. It might be worth allowing the character to apply her DR as a bonus on saving throws against "on-hit" effects. Or simply rule that a hit whose damage is reduced to zero can't trigger effects.

That is a good idea, though it won't completely mitigate her vulnerability since not all hit effects grant saving throws. For example, a T-Rex automatically restrains when it hits with its bite attack, and with its +10 attack bonus will probably be hitting her around 95% of the time. So in certain fights she'll have to accept that she'll be suffering status effects a lot more than her teammates, unless [MENTION=2067]Kamikaze Midget[/MENTION] is careful to avoid using creatures that have automatic on-hit effects.