Ask ten D&Ders how to fix 3.x casters, and you’ll get fifty answers, ranging from “Give all spells full-round casting times” to “Don’t add spell level or ability modifier to spell DCs” to “Casters take damage whenever they cast a spell” to “Make casters spend even more time preparing spells” to “Don’t let PCs buy scrolls, wands, or staves” to “Take away the Concentration skill” to “Give every spell a costly material component” to “Restrict casters to one school of magic” to “Make all casters MAD” to “Ban metamagic and/or item creation feats” to “Don’t give casters extra HP for high Con” to “Reinstate different XP charts” to “Don’t let casters choose their own spells” to “Bring back all those quirky old-school spell limitations like how haste used to age the caster” to “Take away some of their spell slots” to “Take away spell levels 7 to 9 altogether!”
The problem with most of these solutions is that they don’t make casters any less broken; they just make them broken less often. So what if Dominate Person takes a full round to cast, gets interrupted by 1 point of damage, and has a crappy DC just like in ‘Ye Good Olde Days’ of TSR? It’s no less game-breaking when a caster does manage to turn an important NPC or PC into an instant and fanatical ally on round 2. Besides, savvy players will still figure out ways to break the game with the spells, which are just as broken as ever.
A couple of these quick n dirty solutions do help bring casters into line; adjusting spell DCs and/or saves, and adjusting the Defensive Casting formula can only help, for example. But there’s only one real solution to caster brokenness: Fix the spells themselves!
Unfortunately, the real solution is a daunting endeavor. There are a lot of spells, even if we’re just talking core spells, and the system mastery required to hammer them into a semblance of balance is significant. Luckily, there’s no need to go through every spell in the game before your campaign starts, and your internet connection can serve as a substitute for system mastery. So don’t sweat it; tell your players that every spell in the game is subject to retroactive adjustment. Show skeptical and curious players these guidelines, and keep them handy for when a spell gets out of hand:
1. Spells that can duplicate the effect of many other spells are banned. Such spells include, but are not limited to: shadow conjurations, wishes, and miracles.
2. Spells that allow the caster to page through the Monster Manuals and pick a form to take, such as Alter Self, Polymorph, and Shapechange, should be broken up into form-specific spells with predefined effects. Some 3.5 splatbooks have form-specific spells, and Pathfinder has only form-specific polymorph spells!
3. Spell durations should be changed from whatever/level to some set duration. (5 minutes, 1 day, etc.) Buff spells should last for 5 minutes. Spells which create sale-able materials (Wall of Iron, Wall of Stone, etc.) should never be permanent. (I suggest 1 day durations.)
4. Instead of some vague reference to ‘hazards,’ Rope Trick and similar spells should contain this limitation: “Extradimensional spaces are filled with discordant energy. Characters who rest within an extradimensional space do not gain the benefits of doing so.”
5. Every save-or-lose spell should allow a saving throw or some other chance to avoid its effect. For example, you might rule that forcecages can be destroyed with damage, in lieu of requiring the standard ruby dust. (The cages start with 20 HP/level, and can be whittled down from both sides.)
5.1 Powerful save-or-lose spells, like Dominate Person, should allow a saving throw every round to shake off its effect.
6. Save-or-die spells should be ineffective against creatures of similar power than the caster. For example, Wail of the Banshee works normally against creatures that have 5 fewer levels or challenge ratings than the caster’s level. Against more powerful creatures, it merely deals 1d6 damage/level.
7. Long-range teleportation spells work using ley lines, and can only deliver characters to specially-prepared teleportation circles which the caster is familiar with. This prevents caster PCs from short-circuiting entire treks, and allows you to decide where casters can teleport to.
Now that you’ve nerfed the most overpowered spells in the game, you should throw out some of the unnecessary magic nerfs that mostly just punish casual players for not knowing the game inside and out.
1. Arbitrary monster resistances and immunities should be removed. This includes everything from a dragon’s immunity to sleep and paralysis to an outsider’s various energy resistances to many of an undead’s immunity to various effects. (Its immunity to poison makes sense, for example, but there’s no reason it should be immune to mind-affecting magic. Intelligent undead in particular!) In short, any resistance or immunity that doesn’t obviously tie in to a monster’s nature (fire creatures are resistant/immune to fire!) should be dropped.
2. Spell resistance is an unnecessary nerf, and should be removed. Besides, it was never consistent to begin with; acid created by magic is unaffected, while fire created by magic is. Doesn’t make sense at all, once you think about it.
Finally, there are a couple of general rules tweaks that I do suggest making to reign in caster power:
1. Change the defensive casting DC to 15 + double spell level.
2. Change the good save progression to +1 per level (drop the first-level +2 bonus), and change the poor save progression to +0.75 per level.
3. Ban spell and ability DC boosters, and caster level boosters. (Whether they come from items, feats, prestige classes, or whatever.)
4. Force druids to use the shapechange variant from the Complete Divine. (Note that this effectively bans the Natural Spell feat, which is a very good thing!)
5. Ban Quicken Spell and all divine metamagic feats.
And those are all the suggestions I have on this topic. It’s true that casters are fundamentally imbalanced in a way that only a system overhaul can truly solve (hence 4e), but these fixes at least turn 3.x casters from game-breaking godlings to merely great.