In my last RNG rant, I talked about what it meant and how easy it was to do it and how hard it was to actually recognize it ahead of time because you have to determine what a level appropriate bonus even is in your game at your level. I was going to spend this one trying to explain how you determine what that bonus is at various levels and playstyles, but that turns out to be a seriously hard thing to write in a concise or even sensical way because the 3.x system is so broad at this point. And then a conversation over at TGD about the RNG suggested something else I could rant about, namely "when does leaving the RNG even matter?".
Yes, that's right, there are times that you can break the RNG and it doesn't even matter. There are times when you can't possibly fail at a level appropriate challenge and it's not even important or noteworthy. It's very closely tied to the converse, falling off the bottom of the RNG, when your bonus is so small that you can't possibly succeed. It's even really easy to identify these times, there's a one question test and everything. That one question? "Do I care if a character is basically unable to participate in this event?" If you look at a particular aspect of the game that is determined by a single d20 roll, be it a will-saving throw or a full AC to-hit roll or a spot check or whatever, and you answer "No" to that question, that you do not care if some people may as well not even roll for it, you are allowed to break the RNG for that specific check (though you may not want to for other reasons). If you answer "Yes" to that question, you are not allowed to break the RNG for that specific check.
But before we can talk about why that is the case, we should talk about what that even means. Back in the last rant I talked about the maximum bonus you can give to people and keep them on the RNG, it was +8 for checks against static DCs and +15 for opposed checks. That also turns out to be the maximum spread you can allow members in your party to have before someone basically falls off the RNG on one side or the other. If the guy who is supposed to be good at a task is 8 points better than the guy who is supposed to be bad at a task you have a situation where your someone is already at the edge of the RNG. If it's a challenge for the guy who's supposed to be good at it, it's almost in "can't succeed land" for the guy who is poor at it. And it it's a challenge for the guy who's supposed to be bad at it, it's almost in "can't fail land" for the guy who is good at it. You can't actually increase the spread any further without pushing one of those guys off the RNG for the other guy's regular challenges, at which point they aren't even participating in the event. They either win it or lose it, and rolling the die is probably superfluous (auto succeed / fail rules not withstanding). Any bonus that is big enough to break the RNG is therefore also the maximum spread you can have before someone leaves the RNG. Breaking the RNG on the top is just setting the challenge level differently from falling off of it at the bottom.
So, not caring whether people participate in a particular die rolling contest opens the door to allowing characters to fall off the RNG on the bottom or exceed it on the top. Let's take a few examples before moving on. I actually don't care if every character gets to play the "hit the standard AC" game, and I don't care if every character gets to play the "hit the touch AC" game. This means that I can allow players in may games to have to-hit bonuses that differ by more than 8, and players can to fall off the bottom and be basically unable to hit a level appropriate challenge with a sword. I also don't care if everyone can play the "sneaky" game, or the "findy" game, or the "UMD" game so players can have skill modifiers that differ by more than 15. I do care that everyone can play the "make a will save" game, so those bonuses should not differ by more than 8. And so on. The basic system does a fairly good job of working with these answers already. Which is nice, because it means we have concrete examples of falling off the RNG to look at.
Falling off the RNG becuase your bonus is significantly smaller than everyone else happens all the time, and is probably the default case if you don't care about people not participating. Everytime someone doesn't put a rank into a skill or doesn't use a level appropriate skill boosting item, they are falling behind in that skill bonus. It does not take long before they fall off the RNG for level appropriate challenges with that skill. And most of the time, no one cares, because they're optional and not every character is expected to be proficient in all skills all of the time. People care slightly more about hitting things with a sword, and go to great lengths to keep characters closer together on this modifier. For some character groups, this is sort of important, because every character should be able to engage in the combat game in some manner and they don't have access to other methods. But if you can target touch AC or saves or just deal straight damage or status effects, it doesn't matter very much if you can't hit a guy in full plate with a sword. You may have fallen off of the RNG for that set of die rolls, but if you can just choose other options and never have to make one of those rolls it's not relevant to your character at all.
Actually getting a bonus large enough to break the RNG is a somewhat bizarre case, and probably happens most often with to-hit rolls (for a number of reasons). A substantial number of DMs will just scale the opposition up so that you're previously RNG breaking bonus is just a substantial one. This has the immediate effect of pushing someone else off of the bottom of the RNG, but that might be a worthwhile sacrifice if you're concerned about expected success rates. Those that don't scale up the opposition just allow auto-successes, and deal with the fact that the expected success rate is vastly higher than anticipated. Skill modifiers in games with skill item boosters follow the first path actually, dropping those without them off of the RNG as they set the new standards on opposed checks, and plenty of Power Attack builds follow the latter path, with DMs just accepting auto-hits (so the rogues can still get theirs in, don't want them to fall off after all) and players turning the excess bonus into damage bonuses.
These are just a couple of examples of how the game already breaks the RNG in a few places, by leaving it open for people to boost above it or fall off of it. And in these cases it's not that big of a deal. But there are actually places where it sort of fails to do what it needs to. Maybe I'll add those on later, it's already much later than I wanted to be writing this...
Continued!!! Ok, more stuff.
Saves are one of the areas where you probably don't want to let people fall off the RNG. You may have noticed that you could still participate in general in the other areas even if you couldn't participate in a set of die rolls (like in the to-hit game), or it was an optional thing that you would just have to work around (like with skills). Neither of those are true with saves. If you can't participate in a save roll, you're screwed. With few exceptions, there is no backup, there is no workaround, you just suffer and potentially die. This would probably be fine, since a save is nothing but an inverse attack and those can break RNG, were it not for the duration based save-or-suck effects in the game.
The problem with saves is how they scale. There was a longer discussion on that scaling over here (the first section is relevant, before it turned into something else), but for now we'll just say that the peculiarities of multiclassing and save growth rates make it very easy to drop your poor saves off the bottom of the RNG at high levels, and almost impossible to boost your good saves off the top of it without substantial multiclassing. The multiclassing issue in particular allows players to have saving throws bases that exceed the +8 range mentioned above, breaking any sort of RNG you can imagine. And at high levels, saves can actually be really problematic, with a number of characters just plain failing their poor saves against NPCs. Now, some might consider that a feature rather than a failure, but those people also need to have answered "No" to our test question about saves, and I don't think the designers would have answered it the same way. Still, this, like most other things in our games, is a subjective design decision.
You may have noticed that I've avoided talking specifically about attribute bonuses through most of this blog. That's because I don't think they have a large part to play in keeping people stuck on a RNG. They exist to differentiate characters, to put them at different places on the RNG. They should, in large part, not be worked into the scaling rates of things and planned for. If you require their inclusion to keep people in a specific range on the RNG, they have largely stopped doing their differentiation job. You may as well just do away with them and let the scaling level based stuff keep people in the range. The notable failure of that stance is in saves, but I think those are all screwed up in the first place.