This is a bit of a ramble and was difficult to organize. Regardless, I thought it was coherent enough to publish.
The following narrative is to illustrate the subconscious obfuscation of information caused by making everything a bonus instead of a floor.
It’s 1993 and your Fighter is going up against an evil hellspawn. You have a THAC0 of 11 and specialized in your weapon, so you feel pretty confident you can hit him, even at -4 AC and deal some damage. Suddenly, the thing raises a finger and whispers something unholy. The words curl from its lips, mesh with the reality warping from that finger, and a ray shoots forward, hitting your Fighter! Save vs Death or become Disintegrated! You just need a 7+ and you’ll survive!
It’s 2003 and your Fighter is going up against an evil hellspawn. You have a BAB of +11 / +6 / +1. So you feel pretty confident you can hit him at least once, even at a 24 AC and deal some damage. Suddenly, the thing raises a finger and whispers something unholy. Fort Save or become Disintegrated! You have a +7 so you roll and hope you survive!
Base Modifiers Should Not Be Bonuses
Now, I’m not saying bonuses are bad. I’m saying the base modifier for success should not be a bonus. It should be a static representation of success and they should be compared against a fair target — a floor. With the Saving Throws1 in B/X and AD&D, the number itself is the target.
For THAC0, it’s a little more clear except AC 0 isn’t a special number besides making the acronym sound cool. AC 2 is plate mail with a shield. High Dexterity grants up to a -4 AC bonus. So should it have been THAC-2? Or just THAC2? Regardless, it is difficult for anyone to gain an AC of 0. So saying you need a 20 to hit that makes it sound imposing and difficult but at least it keeps an end state in mind.
ACKS simplifies this with doing away with the 10 added to every AC. Now AC 0 means you are naked. And THAC0 goes from 20 to just 10. So you need a 10+ to hit some naked dude. You see a guy wearing plate and you think, “Okay. I need a 18+ to hit this guy.”
Why do it like this? Why not just have bonuses? Because there is no agency without a base score to aim for, making players have no choice but to aim for the largest number possible. It sets them to scrounge for every bonus they can get, always seeking a loose +1 here or there, always trying to weasel something out of some mechanic.
DC and TN Means the Goal is Unquantified
DMs like to keep things a secret. It adds tension, it creates mystery, it forces experimentation. But as characters gain levels, numbers begin to bloat and grow in a bonus centric game. Suddenly they are adding eleven to each die roll and if something changes, they have to short-hand your math or recalculate it to make sure nothing was lost in the process. Players lost a touchstone to reference.
Its not secret that growing numbers and bonuses is a tried and true tactic of casinos, video games, and TTRPGs. It’s crack for people who want to feel powerful but it eventually becomes exhausting. That’s why 5E did away with circumstantial bonuses for advantage and disadvantage. Having a touchstone allows players to reference the floor of success and move from there. Instead of having the +11 base bonus, having a floor to hit AC 0 creates a static starting area. No longer is the D20 the starting number to add to.
Here’s a different point of view. A Level 1 Character can have anywhere from a -3 to +4 bonus to their attack in any edition of D&D. (Technically +5 in Modern D&D.) At Level 5, that same character will have a +2 to +9 to attack. This is including their class’s base to the attack. So where is the benchmark? What is supposed to be average? +0? For who? It sounds like you are a shitty fighter if you don’t have a +5 to hit at Level 1. Because everything is reduced to a total bonus number. And bigger is better.
Since everything is a bonus, the DC and TN are amorphous. It can be a DC 15 at Level 1, DC 25 at Level 5, or DC 35 at Level 10. The difficulty class or target number become larger and larger, more and more abstract.
This base can’t just be the total of all parts. It has to shift and grow with the Character while remaining separate from the bonuses. So that Level 1 Fighter should have a +1 BAB. But what does that +1 represent? A +1 against…? It’s against yourself, your own die roll, the D20. Really, the Fighter should have a To Hit Armor Class metric. And if that happens to be AC 0 in the ACKS sense or the B/X or AD&D sense, so be it. But it should be something apart from the Character’s stats an bonuses and weapons and magic. It should be something at the core that is immutable outside of experience growth.
Abstract vs Objective
All of this boils down to Abstract vs Objective with me positioning DCs, TNs, and Bonuses as Abstract; and THAC0 and classic Saving Throws as Objective. The idea is that eventually bonuses and DCs enter the realm of absurd with no coherent meaning behind them and thus Players are trained to seek the largest number possible. So instead we should have a defined floor of success.
Mathematically, it’s all the same shit. But the representation of the information causes a different thought process to take place. With bonuses, the place to start is always after the die rolls. With a floor or base number, the math begins prior to the roll — it sets a goal prior to the roll, it sets expectation.
Anyways, it’s easy to fix this in every edition. Like I said, the math is all the same.
Some may say it’s not fair that a death ray, power word kill, and a basilisk all have the same save difficulty but there’s where HD and the +/- 4 modifier comes in. And even a success doesn’t mean nothing happens. Often times, success indicates less damage or a shorter time period for the penalty.