It actively frustrates me when I read about something new breaking the RNG or going off of it. Almost never does the person actually refer to the new ways that they break it or why it matters or in what context, instead they only just refer to some nebulous bad that breaking the RNG is supposed to represent. Like it’s a holy artifact to be cared for or looked upon warmly or some crap instead of the fidly, poorly maintained and cared for piece of DnD that it is. So I’m gonna rant about it for a while, and start getting at what it actually means to be off the RNG in a scaling system.
Most of the regulars are familiar with the ideas behind the RNG, and how it’s pretty much broke in 3.x DnD. I imagine that some of our new users haven't heard of it, and I hope this will serve as a useful primer for them. To that end, and because I hate term confusion and want everyone to at least know what page I'm on, history and setup first.
So, what is this RNG thing? It's an acronym for Random Number Generator, and it's a reference to the dice that we roll as part of the game. It could be 1d20 or 1d100 (for flat range systems, like d20), or 3d6 (for bell curved systems, like GURPS or the variant 3.x DnD from UA), or xd6+y (for dice and add systems with tighter, scaling curves, like 2E Star Wars), whatever your damage dice on a hit are, or even a coin flip. If you use something random to return a number that you use in determining the success, failure, or magnitude of your action, you're using a RNG.
So with that general definition out there, we're going to leave behind everything besides the d20 at this point. When people here talk about the RNG, they're specifically referring to the d20 because it's generally the thing that separates you from success and failure in DnD. And it's sensitive, and very, very small. You can add 20 points to your damage roll, and that might make you auto-kill some things you hit but it's not really a big deal at most levels (it might matter at low levels) because you still have to succeed to hit. Adding 20 to your d20 roll is as much as the die itself could possibly add. Adding it to resolve the success or failure of an action might mean that you succeed significantly more than the game expects you to, and that's kinda a big deal. Or it might mean that you're level 12 and just have a bonus that big and need it to even compete at that level. It really depends on where you are in the game, which brings us to a side point that has to be addressed before I can go any further.
3.x DnD is a scaling game. Since monster ACs go up as you advance, you need a bigger attack bonus to hit them reliably. Conversely, since monster attack bonuses increase as you advance and fight tougher things, you need a bigger AC to get the same defensive benefit at higher levels. Since saving throw DCs go up as you advance, you need better save bonuses as you advance. And so on. What the game attempts to do is keep your chances of success stay roughly the same for some things, improve for other things, and decline for the rest as you go from level 1 to 20. By changing the way that your numbers scale against your opposition's numbers, you change the number you need to roll on the d20 to succeed, and thus your odds. The thing is that there's an expected success rate that comes with each level for things depending on how good you're supposed to be at them. That success rate right there is the bit that's sensitive, as that’s supposed to follow a predictable growth rate as you level.
So let’s say there’s something that you’re supposed to be “good” at, it could be combat or stealth or whatever. And you’re supposed to be good at it as you level up even. Let’s call the expected chance of success on standard challenges in things you’re supposed to be “good” at 55%. If you add your level, competence, and balance point appropriate bonuses to your roll, you’ll succeed on a challenge of average difficulty by rolling a 10 or better. This is arguably the success rate for people that are supposed to be “good” at stuff that 3.x is built around, so it’ll do for an example. And yes, this means that the game expects you to fail approximately 45% of the time. When people here talk about being off the RNG, they mean that your bonus is big enough that you no longer need to roll for things that you’re supposed to be good at (or at least you don’t have to roll for them any more than you have to roll for things well below your level), and so vastly exceed your expected success rate. In the case of anything that has an auto-fail on 1 rule, you hit that condition when you rack up an unexpected +8 bonus to your rolls, otherwise it’s +9. For opposed rolls, where there is quite a bit more variance, it’s closer to +16 for math reasons I’m going to skip for now.
+8 is lower than a lot of others on the wiki think can actually push you off the RNG. I can only guess that they're worried about things other than standard challenges at things you are supposed to be “good” at. +8 is not enough to push you off the RNG for things that you're supposed to be bad at, it will not give you auto-successes against difficult challenges of you level or average challenges well above your level, and it isn’t enough for a definition of ‘good’ that involves a 50% success rate or less. The thing is, if those are what you worry about because they’re the majority of challenges that you go up against then they are your average challenge difficulty and you need that bonus to even complete if you’re supposed to be good at them.
As that varies from game to game, this last bit is a balance level and play style concern. Which means that it's probably ok to have higher bonuses in a higher balance level game. And it's probably not ok to have them in a lower balance level game. Or in games with particular playstyles. A bonus might be low in one game and high in another because of differences in balance, even if they’re played at the same level. The bonus itself isn't the problem though, and a bonus on its own can never be a problem without context. Determining the context that a bonus is or is not appropriate in requires a whole other set of concepts and looking closely at the scaling bits of the system, and I’ll save that for another rant.
This is starting to get at why it’s so hard to determine whether a bonus will push you off the RNG or if you just need it to keep up. You can barely even talk about it if you don’t have an expected value for your regular bonus at that level, and yet people do it all of the time around here with all sorts of hidden, unspoken play expectations that would influence the expected bonus values. And differing expectation values make different bonuses perfectly acceptable or completely unthinkable when placed in context. The inherent scaling of the game and variability in challenges faced make it an extremely level and balance point dependent question, it's just rarely phrased that exactly. And it's only made worse because the system hands out bonuses like candy.
So when people start complaining about the RNG without bothering to explain their concerns, I get annoyed. It's a really complex topic that isn't served by not setting some groundwork (which should be expected for a really really integral part of the system) and people don't seem to get that. Hopefully if you read this you understand why I feel like that, and will have an easier time expressing yourself regarding the RNG in the future, especially if you're talking to someone who doesn't share your balance level or play style preferences. And if you didn't understand it, or think I'm way off base, let me know below.