Originally Posted by gmnenad
That is correct, and I'm aware of those - that is why in my post I said that calculating your hit chance ( attack roll ) does not change at all . All it changes is that after you calculate that player has 70% chance to hit, you do not random for hit/miss but you instead reduce damage by multiplying it with 70%.

To be more clear, game already change your hit chance ( shown when you hover over target ) as you change conditions like gain advantage by height or counter disadvantage by casting light on shadowed enemy etc. What will change in my suggestion ( when that option is ON ) is that game will change your expected damage, so it will show for example "3-4" damage without advantage and will change to for example "6-7" damage if you gain advantage - instead of showing hit chance percentage on hover, it will show this expected damage, while still showing reasons for advantage/disadvantage in lower left corner.

I mainly bringing this up because it would be a big time investment for Larian and there are other options to abandoning dice rolls. To reduce randomness Larian could buff base proficiency for player characters or give a +1 modifier to all rolls. That's a lot quicker than rebalancing spells and so many other factors that come up with your proposal.

Scaling damage by chance to hit is still more work than you're making it out to be. You're asking to have all hits succeed (fixed dice), no critical hits, and no zero damage hits. With your proposal you're saying that you would prefer the game if you could never finish combat in one round and you would always take the average turns to win. Variety keeps games fresh and exciting, it's the whole reason people still play card games. The opportunity that you are unsure about what will happen is exciting.

The Importance of Zero Damage and Critical hits
Never underestimate the power of zero in terms of your party's survivability in the game. It's the whole reason the concentration mechanic works in DnD. Adding assured damage will make concentration spells useless. Also taking 5 damage instead of 0 drastically changes decision making.

You will have turns where your party is just chugging potions. Whereas before they would not have been. Never getting a critical hit will also drag out fights longer than they should be and the game will need a rebalance to compensate for all the factors listed above and more.

Now let's talk about the impact of critical hits, for example rolling 1d12 versus an enemy with 24 health and 12 AC. (DnD 5e always rounds down)
<Assured Damage>
Damage range (1-12)
> (no modifiers): 9/20 opportunities to hit, 2 damage per turn, (12 attacks).
> (+2 proficiency, +3 modifiers): 14/20 opportunities to hit, 4 damage per turn (6 attacks).
>now 99% chance to hit, 5 damage per turn (5 attacks).

<Critical Hits, the natural 20>
Damage range (2-24)
> (no modifiers): 9/20 opportunities to hit, 5 damage per turn, (5 attacks).
> (+2 proficiency, +3 modifiers): 14/20 opportunities to hit, 9 damage per turn (3 attacks).
>now 99% chance to hit, 12 damage (2 attacks).
> 1/240 times you could kill the enemy in one hit.

So, having no chance to crit will make combat longer.

Do you really want the trade-offs?
To always take down that enemy in 5-12 attacks while always having to chug potions in combat? When there could have been a chance that you took the enemy down in 1 hit? When there could have been a chance your cleric took no damage and gets to keep concentrating?