Something that bothers me about the advantage/disadvantage system is that it doesn't actually affect how much damage you do in a single attack, only the likelihood that the attack will hit. For example, when I think of a Barbarian using Reckless Attack to "attack with fierce desperation", I don't think of that as a precision strike; rather, I see it as an attack that should have just as much chance to miss, but hits like a freight train if it hits.
Based on this, I had the idea to change how advantage works for some attacks. The new rule (let's call it damage advantage) would work like this:
- In all cases, the attack roll is unaffected (that is, roll one d20 and apply any attack roll bonuses that apply).
- For damage rolls that take 1 die, roll two dice and use the higher number.
- For damage rolls that take more than 1 die, roll an extra die, and drop the lowest number. This applies to things like the greatsword, as well as for critical hits.
- Other special damage modifiers (sneak attack, magical effects, etc) are unaffected, but for the purpose of this question can be disregarded. My main concern is 'normal' attacks made with advantage.
What I'd like to know, then is how damage advantage would compare to attack advantage in terms of average damage dealt. The part that I'm having trouble calculating is how this would scale as PCs level up, and against weaker/stronger NPCs. Essentially, low/high attack/damage bonuses vs low/high AC. I'm hoping that damage advantage should excel in some circumstances while attack advantage should excel in others, but I want to ensure that overall, assuming an even distribution of combat scenarios, both systems should turn out to be equally useful, so that at the end of the day no character should feel that their advantage rolls were nerfed or that another character's rolls were buffed.
Whether or not damage advantage would be fun/confusing is beyond the scope of this question. I just want to ensure it's balanced.