Slowing down progression for skills isn't the biggest problem, it's the stats that lead to too much bonuses mostly. Everyone is min-maxing and gaining ridiculous bonuses. I'm trying to lessen them and penalize min-ing.
Maybe you should replace attribute numbers and modifiers with modifiers and exp, with higher levels costing more.
So for instance, currently every 8 SLP you gain 2 stat points, and every 5 or 10 points you gain +1 to related rolls. What if instead, every X SLP you gained Y stat points, but the points needed for your next +1 depended on what the bonus was already at. Maybe to go from +0 to +1 took two points, +1 to +2 took four, +2 to +3 was six, etc. Eventually you'd get to the point where players would have to ask themselves- do they want another +1 to spellcasting, or +4 to dodging?
The only trouble, of course, is that progression would slow down. Potentially you could do it in reverse- your other stats get cheaper the higher the ones you're buying are- but that might be a bit wonky.
You're underestimating the problem. On a LR of 1, bad things happen. On LR of 2, your roll fails, no matter how good it was. On 3-5, nothing changes, good or bad. On a 6, bad things happen. You have a 1/3 chance of screwing yourself and the other players over and a 1/6 chance of wasting your turn, which is almost equally as egregious.
Whoa whoa whoa, I object to a lot of that. There's a difference between 3, 4, and 5, and a 6 isn't just a 1 in disguise- it's so good that it has consequences, not just lol u fail. There's a 1/6 chance of screwing yourself over, a 1/6 chance of wasting your turn, a 1/6 chance of kind of doing some of what you wanted, a 1/6 chance of doing what you wanted, a 1/6 chance of doing even better than expected, and a 1/6 chance of doing more than you wanted to the point where it might be a problem. Sure, that leaves a 1/2 chance of something "bad" happening, but at least a 1/2 chance of something good, and more like 2/3 that you'll make progress.
More to the point, though, I'm not sure what this has to do with luck as opposed to rolls in general.
Failing a normal roll is just a failure; I rolled a 1, I can live with that. Even if I'm trying to cast a hard spell and the resulting negative modifiers take me down to where it fails, again, that was my choice to try it and I've got no one to blame but myself. But if I roll really good, if I cast that +3 spell and make it, I WANT THAT SPELL. I DO NOT WANT TO SEE AN ARBITRARY 1 OR 2 SPRING UP AFTER IT AND WASTE MY TURN OR HURT MY ALLIES. It is not fun or entertaining; it just sours my mood and makes me wonder why I should bother continuing on.
To go back to the Westlands, I can take Chaos Mutations. That's a penalty for doing dumb things or hanging around irradiated areas, and it's only temporary if you want it to be/survive long enough to where you can get rid of them. No problem, if you get one you like you can even keep it. Powerful spells have such high modifiers you need a high skill to cast them. Again, no problem, if you wanted to cast them start with weak ones and work your way up.
Again, you're very clear that you loathe bad luck rolls, but make no real mention of how they're different from
regular rolls gone awry. It sounds like you either feel you're being taunted by having a high roll within a bad result, or simply object to the notion of having to roll at all. If it's the former, I'm not sure how that's different from rolling a high attack roll but having your enemy roll a higher dodge roll (or vice versa). I'm not sure how it could be the latter.
The problem comes from the fact there is absolutely no way to prevent bad luck from happening. I would gladly take a 'luckless' penalty that completely prevented me from, say, doing critical hits if it also prevented me from ever needing a single luck roll.
Well, let me ask you then- how would you feel about a 'rollless' penalty that stopped you from
ever failing by simply automatically accomplishing what you should statistically do per turn?
I think you're overstating this. You still get stronger, there's just always a chance of failure, catastrophic or otherwise. I mean, would melee combat suck if there was always a chance of missing, no matter how much damage you did on a hit?
There's already a chance of failure. You don't need to stack the deck even further. For example, CvRTD: Ahra's got a mighty +4 defense. He can still be hit and killed. I don't need to add an arbitrary luck roll to the enemy attack, whichwould be like: 3 vs 7+4; Luck 5, looks like your defense doesn't matter at all because this second roll here was good, and you have no chance of countering it or blocking it or doing anything about it. You get hit and that's that.
Again, I'm not sure how this differs from: 6+4 vs 8+3; aw, you missed, looks like your attack and damage don't matter at all because the second roll here was good, and you have no chance of following up or attacking again or getting ready to counter or anything. You miss and that's it.
I would also like to point out that every one and thing in the game is beholden to the same rules, so it's not like your enemies would be wearing a trollface, flawlessly casting spells at you while you fumble yours because lolplayer.
If I was him I would feel bitter about it. A stupid little arbitrary number completed negated all the time I had put into that character, and made it pointless to raise his defense.
Again, this section is pretty much perfect for replacing "luck roll" with "skill roll" to get the same result. It's not pointless just because it doesn't work every time.
Now if Malleus were fighting a powerful enemy and the rolls went 6+3 vs 3+4, if I was his player I wouldn't mind that as much. Eh, it's a powerful enemy, of course it's going to hit every once in a while. The difference is small, but it's distinct. It's true that for specializing so much he suffers in other areas; if he gets into a situation where he needs to be mobile he's going to suffer severe penalties, but that's how he built the character. If he falls to his death it's not because he's playing some epic level acrobat who rolled bad on his luck and died jumping from platform to platform when he should've been able to clear it, even if only by a little; it's because he's a knight in heavy armor trying to jump from platform to platform when clearly he couldn't make it but chose to leap anyway.
For anything that isn't guaranteed- that is, doesn't need a roll at all- there's still going to be the chance for Malleus to get hit by 8-2 vs 1+4, or a legendary acrobat to roll 1+9 vs DC 12. Either is going to be infuriating, because either is extremely unlikely, but that doesn't mean it shouldn't happen, or else, as I've said, it just means you didn't need to be rolling for it at all. Same thing with rolling poorly several times in a row, or an enemy rolling well in succession- of course it's "not right" on some level, but would you advocate disabling that somehow?
Furthermore, we're mostly talking about internal rolls here. It's not a goblin running up to you and forcing you to make a not-die check that you're unlikely to pass, it's you deciding you want to make some lava or summon a dire wolf or suck the life from an enemy, and then either succeeding to various degrees, failing, or occasionally making things worse as the dice command.
I don't know if I'm stating my point clearly or not, but I hope so.
You're getting across that you're frustrated and infuriated by luck rolls quite well, but the exact reasons aren't quite so clear. It sounds a lot like your issue is just that the odds are too low- you feel a warrior should hit at least X% of the time or dodge no fewer than Y% of the time, and luck rolls take casting beyond acceptable limits. There's heavy, heavy overtones of them being unfair in some manner beyond that, but you're not really explaining the difference between, say, 50% skill hit and 50% luck hit, and a flat 25% hit chance. You also seem to say that Die+Modifier is acceptable but Just Die is unfair, but again don't really distinguish between different methods with the same odds. I guess I understand that rolling the [5] in [5][Luck 2] is irritating, but I've never considered it "I've been cheated" or "The GM/RNG is making fun of me" level enraging, and as mentioned you don't explain how it's different from the [5] in [5] vs [6].