The obvious solution to this problem is to prevent the RNG from shifting too much. Yeah. This solution is doomed to fail from the start. Let's talk about why it will fail and why the proposed solutions will fail.
1) People wank too much to the idea of there needing to be 20 levels of advancement. The existence of E8 and epic show that people don't necessarily want their characters to transform--they just want their characters to get to level 20. Amazingly enough people don't really care that the upper limit of advancement is something stupid like 30 or 60 levels. 20 seems to be the bottom limit for some retarded reason.
2) This wouldn't necessarily be a problem in of itself, but some people seriously think that Conan the Barbarian or Lord of the Rings (not the high-powered stuff, just the bullshit low-level crap) has enough content in the game to have 20 levels of power division to the point where someone would notice in a narrative context. Sure, I think that if you were designing a Dragonball or a One Piece or a Marvel Super Heroes game you could definitely have a recognizably different archetype/iconic for each level of play. I mean in Marvel Super Heroes the difference between a level 14 superhero and a level 18 superhero is Thor and Silver Surfer and you can definitely see a difference in capabilities and ability to affect the plot. But for Conan? If the top end of power for that game is friggin' Thulsa Doom, what's the difference between a level 14 swordsman and a level 18 swordsman?
3) This again wouldn't necessarily be a problem in of itself, but people demand that substantial amounts of stuff be given to players in every unit of advancement. Hey, I don't have a problem with that. If a gaining a level didn't give me anything I wouldn't want to gain it either.
But remember, we're operating under the assumption that 1 and 2 are true. I've heard on these boards time and time again that people want to have 20 levels so they don't feel like they're advancing too fast. But they ALSO don't want to go beyond Conan level.
So you know what this means?
HUGE AMOUNTS OF LEVEL FILLER IN THE FORM OF RNG FUCKERY
That's fucking right. You know how 4E D&D constantly kvetches and crows about how 'everyone gets a new thing to do every level'? Well, that's because most of the things they give are cynical manipulations to the RNG. It'd be false to say that the schticks of a 30th level 4E character are always the same as a 1E character, but let's look at the limitations for high-level powers in that game.
- Characters are almost never allowed to get powers that alter the course of the plot.
- Combat is supposed to take place in a 20' x 20' x 15' rectangular prism at the absolute maximum. At all stages of play.
- 'Hit it with a sword' is always supposed to be a viable solution to problem solving. So challenges must be nerfed so that a really good swordsman with the capabilities of a mundane human can solve the adventure. Seriously, look at some 4E published adventures (Tomb of Horrors and Attack of the Frost Giants is a good start) if you don't believe me.
- Schticks gained at level 1 are supposed to be viable throughout the range of the game. Spider-Man kicking people in the face by swinging on a web is always supposed to work, even at level 30.
But they still have 30 levels to fill. So they HAVE to make the numbers bigger. Heroes aren't fundamentally different, they're superficially different!
4) 1-3 is enough to break the RNG of most games. But still, in theory, it's not impossible to have all of these things built together and have a balanced game. After careful months of playtesting and math-hammering, you could design a game where the RNG doesn't diverge despite peoples' numbers continually increasing. You just have to really control the inputs.
But you know what? That's just not possible for a game like D&D. People can just NOT RESIST having a bunch of shit stapled onto their character. This goes for both players and writers. The easiest way for anyone to have a game effect that people will notice is to attach a number to it. No one gives a shit about the rituals in the Forgotten Realms Player's Guide, but everyone and their mother talks about Dragonshards. If Unearthed Arcana didn't have Hybrids, flaws, and bloodlines no one would give a shit about it. Song and Silence is the least popular of the 3E classbooks because it doesn't have any new numbers in it.
Even if you had complete editorial control over your product, there's no way you can prevent power creep unless you're willing to sacrifice sales at the cost of number control. You have to account for it. But again, you have 20 levels worth of content to fill. And most people play in the early stages of the game. Just fucking LOOK at all of the RNG-fuckery stuff available for 8th-level characters in 4E D&D who picked it up Summer 2008 versus summer 2010. And that's only after two years. Would anyone really have picked up Adventurer's Vault 2 if they didn't have item sets and new item slots? Would anyone have given Eberron Player's Guide a second glance without some of the RNG-fucking PPs and items?
If you have more levels to put into your game, people will come up with more ways to fill them with content. This needn't necessarily be bad. The problem, unfortunately, is that even though people would think that it would be really cool for Conan to have a library of a hundred magical swords to choose from, the swords aren't allowed to change his schticks. So you either have to print nothing but trash drops (which will kill sales) or you fuck the RNG in the long run.
5) A less obvious, but still fail solution. Normalize the RNG at certain points in the game. This means that at level 15, your swordsman swinging a sword at +25 to hit suddenly drops down to +5 to hit when they get back to level 16. Did this mean that your swordsman became weaker? No. He is still better than a level 15 swordsman; it just means that when he fights sub- level 16 swordsmen they're cannon fodder who don't deserve large spots on the RNG. But since the L16 swordsmen are now also fighting level 16 enemies, that bulge of twenty points doesn't mean anything. So you might as well take it off from both ends
This is again a non-starter for two reasons.
5A) People insist on bonuses being the same relative bulge of advantage at all levels of play. From a narrative standpoint there's really no right way of saying whether minor bonuses should or should not count. I think it would be insulting if Captain America's major enemies got a huge boost in durability just by finally wearing some mundane armor, but on the other hand some people still want 'I have the high ground!' and 'that kiss my sweetie gave me gives me a +2 bonus to attack, which is enough to defeat you!' in the game.
Regardless, however you feel about it this STILL fucks up game. If you're playing the Incredible Hulk, you will always notice that +2 Gauntlets of Strength makes you kick more ass unless you're already off the RNG. People can whine about 'Christmas Tree Effect' all they want but the basic problem is that people still want that orphan's trinket to matter, so we'll always be mowing down weeds without pulling up the roots.
5B) If you're playing Marvel Super Heroes, no one is really going to care that you normalized the RNG. Once you start hanging out with Dr. Doom and Magneto, you're not going to care that your attack bonus dropped from +30 to +10, because in exchange for 20 points to attack with your adamantium claws you can now slice your sword hard enough to cleave a building in twain. Only a fucking nerd would care more about the number loss than the schtick gain.
Except that... we're not playing Marvel Super Heroes. We're playing Conan. Level 11 heroes still do pretty much the same shit as level 16 heroes. When your bonus goes from +30 back down to +10, people feel neutered. They're still the same character, it's just that for some reason their sword doesn't provide as much of a RNG bulge as it did in the past. You don't GET any new schticks to compensate for the fact because otherwise you wouldn't be playing Conan.
Thus RNG adjustment is impossible. Too many people will just not be able to suspend their cognitive dissonance enough to realize that it's good for the game even though their numbers (which don't mean fucking shit) down. Fuck, man, people might even get all butthurt and whiny at the unwanted but totally true realization that making their levels go up is pointless.
So we have eternal RNG fuckery.