All of the other forums argue about casters vs. mundanes in terms of damage output, which is missing the forest for the goddamn trees. The biggest disparity is one of agency.
Magic guy decides that he wants to go on vacation in the 9 hells; he memorizes the appropriate spell and leaves first thing in the morning.
Sword guy decides that he wants to go on a vacation in the 9 hells; if he doesn't have a caster friend on hand to send him there, he needs to go on a quest to find someone to cast Plane Shift for him, then hope he finds someone to do the same on the other side after he's done fighting monsters that he can't kill without magic, or else he'll have to find an apartment and an air conditioner.
You can't really even out this disparity while keeping sword guy just a blue collar Everyman Joe who 'Mericas good, even in geezer edition D&D when he controlled armies; because they had to march, make camp and die of dysentery along the way to the story, unlike the Pit Fiends that the book nerds can summon.
So in this regard, I agree that the game needs to accept that sword guys eventually become Gilgamesh, Hercules, Cuchulain, Reynard the Fox, et al. That's #1.
Second, I agree with the idea of Rituals. Not the implementation mind, but the idea of separating big, campaign-buggering, Gordian Knot cutting powers into their own resource management category. And don't just charge a sum of fucking god to use story powers; make the cost some sort of group wide resource so sword guy is actually contributing in some small way, even if he has to jerk off into the cauldron to fuel the time portal with his (or her) manliness. That, or make the reagent cost a bunch of quest items that need to be adventured for.
Third, the game needs to tie magic guys to the same attrition model that sword guys are on, because as it stands now casters don't give a wet shit about hit points: they get to bypass those altogether. Or, the old attrition model needs to go entirely, and instead sword guys and casters just knock their target up or down a condition track or some shit.
Fourth, the scope of casters needs to narrow. Magic guy essentially gets to change his class each day, instead he should specialize. You could tie them to spell schools like Divination, Conjuration, Enchantment, etc. or tie them to themes like necromancer, pyromancer, summoner, you get the point.
In any case, this is not going to look like the 3E wizard that people know and love...but if you want to swing your magic staff around like a big, knooted, rune etched dick substitute then play Ars Magica. In summary:
- Martials get supernatural abilities at some point.
Reality fucking powers become rituals instead of just spell slots.
Spell slot attacks follow the attrition model, or cause short term tactical effects.
Casters become more focused and specialized, and not Batman.
The most dangerous game is man. The most entertaining game is Broadway Puppy Ball. The most weird game is Esoteric Bear.