Some counter points to Hejdun's earlier comments.
Disclaimer: I am reaching a conclusion that no amount of well worded anecdotes or number crunching or debate will fully overcome any gamers in game experiences.
1. Anything you can do, I can do better.
Possibly true, but why would you want to? One example that's been thrown about is that Wizards make better scouts than Rogues, because they have Knock, Fly, and Invisibility. Yeah, Knock is better than Open Lock, but the Rogue can open as many locked doors as he wants without giving up any resources. Each single locked door/chest a wizard wants to unlock costs a 2nd level spell (which you'll have at max about 6 of). So on our scouting expedition, you're looking at expending a 3rd level spell (fly) and a ton of 2nd level spells (multiple Knocks, Invisibility, Silence) just to do what the Rogue can do all day long. And you still won't have anything that can see or hear enemies before they bash your head in, because the Rogue's Spot and Listen are way better than yours.
The reason casters often have the option of doing this in practice is because of two things; The 2 hour adventuring day, affordability of low level scrolls, and the general ineffectiveness of low level spells vs level appropriate opponents. The Rogues spot and listen are better than the casters, but the casters Invisiblity and Silence type spells are better then most opponents Spot and Listen rolls, so the point is moot.
Yeah, a Cleric could become a better fighter than the fighter, but only for 2 combats a day and only if you give him 4 rounds to cast all his spells first, and only if the enemy doesn't see him glowing like a Christmas tree and cast a dispel magic on him.
Not all CR appropriate opponents are going to have access to dispel magic, especially if the DM prefers to use monsters without class levels.
2. Save or Dies make fighters expendable.
A single Save or Die has a very, very low chance of actually working against an enemy that matters. First of all, CR=level monsters with spell resistance have at least SR at least 10+lvl, so that means you're looking at a 45-50% chance to fail against spell resistance minimum. Yeah, you could take Spell Penetration and Greater Spell Penetration, but those cost 2 feats and only give you an extra 20% chance to succeed. Yeah, you could use Assay Spell Resistance, but those burn up 4th level spell slots mighty quickly.
Fair point. However CR appropriate opponents without Spell resistance only have saving throws.
And even if you beat spell resistance, you still need the enemy to fail their saving throw. Again, if you're attacking an enemy that matters, their saves are very, very good. You're only looking at a 10-20% chance that the enemy actually fails their save. So yeah, Save or Dies are great the 10% amount of times they work. The other 90% of the time you're just wasting resources. Save or Dies are really only good for when you're getting overwhelmed with medium threats that you have a decent (50%+ chance) of killing right away before they mob you. If you want to pull off a Save or Die on an important enemy, it'll take multiple rounds of stacking Enervations on them to give your SoD a chance to succeed.
Save or Die spells are viable whenever the player has the means to either pump up the DC of the required saves, and / or use spells that target a weak saving throw. However, the usual complaint about Save or Die is from players, not DM's. Players tend to be unhappy when a single die roll can screw them. I would agree that on the whole such spells are balanced.
3. I can just cast an "I Win" spell.
Pretty much every "I Win" spell is either very conditional, easily prevented/reversed, or has various other reasons why you wouldn't want to cast it all the time. Take Forcecage, for instance. It costs you 1,500gp a pop, which isn't peanuts even to a high-level character. It can be quickly bypassed by a lot of enemies. It doesn't do anything to actually kill the enemy. It's Close Range, which means you have to get in, for instance, breath weapon range of the dragon.
"I Win" spells are generally conditional in such a way that they are useless against some opponents, but are very often going to be quite useful against many other possible opponents. Force Cage may have shortcomings, but it is still very viable against a dragon. Breath weapon may suck, so that just means you first make sure you have sufficient resistance to the breath type before you get in close. Cost of components is generally a lousy way to balance a spell, but getting gold is hardly a problem at higher levels. It may not be cheap, but it wont make or break the players either.
4. I'll never actually die because I have Contingency.
First of all, there's a million things out there that can kill you, and you only get one Contingency. And even if you're lucky enough to pick the one situation that you happen to run in to, it only saves your neck once. But secondly, every single defensive spell you're casting is taking the place of an offensive spell that you could be casting instead. So yeah, you could buff yourself to the gills, but it'll cost you a good chunk of your power to do so.
The simplest use of Contingency is to guarantee an escape given a precondition. Yeah, it can be worked around. But it can still save the caster precious actions in combat. Why prebuff when you can just in time buff.
[/QUOTE]
In Conclusion
In reality, I never had nearly enough spell slots to do everything that I wanted to do, or wished I could do, or needed to do. And you always had to pick exactly the spells you need for the day in advance, meaning that every wrong choice materially decreases your power. The Paladin in our group was extremely important even up to the last combat. We'd frequently get into a situation where we'd be fighting enemies who I could try to blast, but doing so would take 2-3 high level spells that I would really like to save, and I'm not even sure if it'll work, and the Paladin can chew them up in a few rounds anyways.
Secondly, you aren't acting in a vacuum. I spent a lot of my time Dispelling Magic because we were fighting something that kept throwing Blade Barriers in the way, or trapping us with Walls, or going Invisibile. At least half of time in combat was spent countering enemies' abilities instead of setting up my theoretically awesome combos.[/QUOTE]
Wizards who make a habit of creating spell scrolls will circumvent the problem of needing to memorize a spell that they may absolutely need but are not likely to use. While there are some spells that are obvious wrong choices at time, some spells are never the wrong choice. Most wizards have a semi-standard selection of spells that sledom change, outside of some customizations specific to the current adventure. The DM will know what the fighter is capable of for most of the adventure, only having to update this when the character levels up. Characters with mutable spell selections are much harder to account for.
You do not act in a Vacuum, but neither does the DM. It is very difficult for a DM not to metagame to some extent. They may not hyper optimize encounters to screw the players (at least the good ones do not do this). But they will often make sure to avoid encounters that they know will be a waste in time. A DM only needs to be burned really badly once to start avoiding things that just will not work. The DM generally wants to challenge the players, and it simply takes much more work to make sure that the Wizard and will be challenged.
END COMMUNICATION