The issue is that people are too scared (this includes devcat) to make sweeping balancing changes. The following thoughts are ones I've made plenty of before but I'll throw some together. The first thing we need to establish though is that Puppetry is an absurdly broken skillset and any balance discussion should start with "nerfing or deleting Puppetry" or it's hard to take it seriously.
-Remove talent stat boosts (including music buff effect/duration and everything else)
-Give all dungeon/SM bosses advanced heavy stander
These are horrible, stat inflation is not good but gutting talent stats hurt classes disproportionately (alchemy barely cares, range is hurt bad, melee barely cares because it runs off high base and multiplicative damage etc) advanced heavy stander is fake difficulty and should be deleted if anything.
The first step to balancing the game is to stop pretending that Puppetry is balanced and gut/delete the skillset until it's reworked. That solves a HUGE amount of the game's issues instantly and makes a lot more content challenging.
The second step is to gut all the hyperscaling multiplicative damage OR create content that can actually deal with it. I think this issue reached its nadir with Frenzy where you essentially have a 312% multiplier on attacks running off potentially 2k max damage and firing at extremely high speeds. Make Overture and Bone Drag chips give flat max, normalize stat gain to attack gain at 1:4 (Fighter would get about 150 more Will to compensate, and maybe higher multipliers).
Also switch Ninja's Will and Str gains please.
In general Close Combat (even if it is just Lances) really should not be this powerful while being so strong early. I'd also consider removing Shields entirely - they're useless outside of PVP, except if you're a giant in which case they're free defensive stats.
Elemental Reforges only need a moderate nerf, maybe to 8% per level.
Piercing actually isn't a problem but what is a problem is that there's no penalty for choosing lances over other damage options.
Magic Weapon Mastery needs to be heavily nerfed (50% maybe) , and magic should get % based buff scaling and higher coefficients on its AOEs (Fireball needs buffs no matter what, and even the cast speed issue is managable seeing it railroads you into just having Fireball available) instead of having those buffs compounded as a compensation buff, as well as making Hailstorm more usable without Crisis in some way. This is only as part of a larger campaign of bringing characters in line though. Though the issue with Firebolt is not so much it's power but it's speed, it's far outclassed per hit by nearly all single target DPS options but endgame Firebolt can fire at close to AR speeds).
Fighter should have lots of single target DPS, nearly as much as range, and more than range for most of the game but gets outscaled at a certain point.
Range would need a compensation buff but I'm not sure what. I think they should be the highest sustained single target DPS class in the game. I'd also like to nerf Crash Shot. How about Bow Mastery, Crossbow Mastery and Ranged Attack getting higher crit caps and crit modifiers (5% crit cap, 10% crit modifier at r1 each, and the Sniper gives 5% crit cap modifier), Magnum Shot goes to 600% base multiplier?
Buff monsters base stats by 2x and bosses by 4x and make them more aggressive on higher difficulties. Swarms can still be hard to deal with, especially with puppet gone, and your best means of dealing with them is Alchemy or trying to protect a squishy mage. Add more skills as well.
However by making content more challenging, imo you also need to make content more rewarding. You're not gonna be able to blaze (literally) through Martial Arts in 10 minutes anymore. So I'd increase all mission base rewards by 2-4x, and make Martial Arts 1-7 a single mission that you can use crystals in, then you exit before the final round. This also increases the difficulty as you only get a few seconds to rest between rounds and rewards greater preparation. Also life skills should be buffed but if you want to go pure combat, you shouldn't be railroaded into life skills for stats. So make life skills more economically viable but remove the stat gains.
Basically the goal is to get rid of clearly game-warping skillsets (Puppet), balance out power curves (Close Combat), clearly define skillset niches that they can specialize in while reducing their power in non-niche areas (Range, Magic, Fighter), reduce the impact of % based scaling (every class except Magic/Alchemy), and increase the overall difficulty of the game across the board (more so for endgame content) while making mid and early game rewarding enough that the average player isn't frustrated with slow progress. We should by no means be trying to kick players back to the bad old days of having to take several months to cap a skill, which I think hurt the game community severely by pigeonholing a lot of players away from combat because they lacked the time and money to get even moderately good (Mabinogi should allow you to do what you want but if the combat aspect is so frustrating that players would prefer to socialize to the total exclusion of fighting simply because fighting is too frustrating or you get stuck in a rut because leveling a skill once takes a month, then that should be - and was - fixed.)