Would this hit/miss houserule be balanced with bounded accuracy?

Question

Would this houserule be balanced with the bounded accuracy system?

If an attack roll is made and "misses" by one, the defender takes a glancing blow. This glancing blow does not count as a successful hit. This glancing blow deals half damage of the attack to a maximum of 3. This damage cannot be augmented in any way. (ex. Sneak Attack, Divine Smite or GWM) This damage does not set off a spells damage. (ex. Wrathful smite) This does not count for reactionary spells. (ex. Hellish Rebuke and Shield) This would count as taking damage for maintaining effects like Rage. A roll of 1 on the die is still a critical miss.

This houserule is for players, enemies and NPC's alike. What's good for the player is good for the DM and vice versa.

The goal of this is to make battles feel more realistic. In D&D 5e you either "hit" or "miss" but in reality you could hit the person and do very minimal damage while glancing off armor. This would apply for any physical attacks. Whether from a save or a roll.

Answer 1

Is it balanced?

Sure, it's balanced if you apply it to all sides of a combat equally. It's a very minor change. Even taking into account characters with multiple attacks each round, it's a couple of HP here or there - not worth worrying about.

Is it worthwhile?

No. You're adding complexity in the pursuit of verisimilitude. That's a fine idea, except that your method goes against the basic system design - D&D5E is not a margins-of-success system, it's a pass-or-fail system. There are other systems where the core mechanics include margin-of-success and have your glancing blows built in. That said, I don't think it adds enough verisimilitude to make the complexity worth while - you're adding an additional parameter check for a whole three damage.

D&D is not a reality simulator.

What you should be looking to do is describe your combats differently. Look at some real sword fighting if you can, or some Hollywood sword fighting if you can't. A sword fighter doesn't swing once every six seconds.

In D&D, one attack roll represents a series of swings, backpedals, feints, dodges, and the glancing blows you're looking for. It's all aggregated into a single roll to keep complexity down. Even "Extra Attack" isn't really extra attacks, the character isn't swinging significantly faster than they were before, but they're so good they can get in more blows that matter.

In the PHB (page 196) we have:

Hit points represent a combination of physical and mental durability, the will to live, and luck. Creatures with more hit points are more difficult to kill. Those with fewer hit points are more fragile.

In other words, it's possible to lose hit points without taking any penetrating injury, from a glancing blow. Take a character with a shield: sometimes, the "hit" that "gets through" is not actual wounds, they're an expenditure of energy and effort in getting the shield in the way or the pain and discomfort from the enemy wailing on the shield. In a similar vein, a "hit" on a lightly armored character could actually be a "miss" dramatically, but the character twists or over extends something in the effort to get out of the way. It may not even hurt right now (adrenaline and all that), but it'll hurt later.

Answer 2

It slightly favors certain character types

I agree with T.J.L. that this won't make any PCs dramatically more powerful or break bounded accuracy, and also that it's probably not worth the complexity. But since you asked about balance, I also think it's worth noting that this rule doesn't apply equally to all character types.

Most obviously, the houserule benefits martial characters that make attack rolls and gives nothing to casters that rely on spell saves. (It's not clear if this would apply to casters that make attack rolls, like warlocks). In previous additions, a power boost for martials might have felt appropriate, but in 5e it's probably not necessary.

Beyond favoring martials over casters, it also favors certain martial classes and builds over others. Specifically, characters that make many attack rolls will see this benefit come into play more often. In most cases, a character has a 5% chance to miss by exactly 1. That may seem quite rare, but consider that a level 11 fighter with the Polearm Master or Crossbow Expert feat can reliably make 4 attacks per turn, which means these characters will see this benefit on average within the first 3 or 4 turns. This corresponds to a damage bonus of 0.6 per round- not huge, but fighters with these feats can already be some of the strongest builds in the game, and they don't need an extra damage boost. Moreover, other very powerful feats like sharpshooter and great weapon master will become even more attractive as the cost of a miss goes down. By contrast, a rogue which makes only one attack per round may not score a single glancing blow all day, especially if they frequently attack with advantage.

The change is admittedly not very significant, so if you and your players really think it will increase your enjoyment of the game you can add it with little fear of breaking anything. However, you are proposing adding additional complexity in order to give a small damage boost primarily to specific character builds that already excel at dealing damage. I would recommend against adding this houserule.

Answer 3

D&D already does what you want it to do.

Roll a hit but not deal much damage? That was a glancing hit.

Hit, miss, and damage are all abstractions of the game world

A hit doesn't necessarily mean physically striking an enemy in a weak point. Yes, it could mean finding a chink in their armor and thrusting through it, but it could also mean smacking them right in the center of their breastplate, it could mean smacking their pauldron and having your attack bounce off, it could mean missing entirely but intimidating the foe.

A hit, or miss was rolled, X damage was rolled. What does that mean in the game world? The DM just needs to narrate the results in a realistic way.

Answer 4

A few notes expanding on @Joe's excellent answer:

The most obvious impacts are likely to be:

• Average damage vs large things - almost nothing: 5% chance to do 3 damage -> .15 extra damage per attack
• Party is advantaged - even up through 10th level, many mooks die from overkill, and a little +3 damage hit may save an attack that usually does 10, perhaps a 20-50% increase.
• "Concentrators" are disadvantaged, every weapon is a +1 weapon in terms of concentration checks
• Multi-attackers (PC Monks, mobs, Hydras) are advantaged. When your build is based on many attacks anyways, free damage is great