A frequent commenter has asked why I would want to take away spells which cause direct damage. It's a good question, and one about which others might be curious too, so I thought I'd blog my thoughts on that subject.
So, why do I want to take away the magic-user's potency in deadly combat?
1) I want something that better matches the wizardly archetype in literature and folklore. Outside of D&D, how many wizards are incinerating foes in battle? Barring the obvious example of Tim the enchanter from Monty Python and the Holy Grail, I can't think of many. Merlin's magic is extremely subtle. He doesn't blast Arthur's enemies with lightning, but he is nonetheless an important figure in those tales. Gandalf knows spells for light and opening and sealing doors, and he's been seen to set pine cones aflame and hurl them at goblins and wolves. Most of his magic is much less flashy. Even in the wizarding world of the Harry Potter books, where wizards throw around spells with no discernible limits to how many or how often they can cast, stunning, paralyzing, and disarming spells are used a lot more often than spells that cause bodily harm.
The wizards, witches, and sorcerers of literature and lore aren't nearly so direct as a fireball in your face. They're subtle, guileful, mystical, and uncanny. They influence and manipulate, enlighten and deceive. Make them angry, and they might turn you into a toad or give you the evil eye. They don't blow stuff up.
2) D&D is about a lot more than fighting, and fighting is about more than just inflicting points of damage. I think the impulse to ensure that every class is effective at dealing damage is misguided. There is already a class that specializes in dealing damage: the fighter. Other classes can do it too, but are less capable, just as the fighter is relatively less capable at sneaking, healing, gathering information, and so on. Every class can contribute to almost every situation, but not every class has to be equally useful in every situation. If a character wants to contribute to a situation that isn't his specialty, he can do so through creative use of abilities, whether we're talking about the fighter helping out in negotiations by being intimidating or the mage flinging utility spells to give the party an edge on the battlefield.
There's a lot that a spell caster can do. Besides their usefulness in non-combat situations such as exploration, information gathering, and negotiation, there are many ways for a spell caster to contribute to success in battle without directly dealing damage. Without an arsenal of magic missiles and lightning bolts, what's a wizard to do? Quite a lot, actually: Terrify and confuse the enemy with illusions. Beguile it with charms. Rescue the fighter in trouble by casting invisibility on him from a distance. Protect your allies with defensive and misdirecting magic. Polymorph the black knight's sword into a bratwurst. Hex foes with bad luck. Turn them against each other with a spell of confusion. With a little imagination and a decent selection of spells, the possibilities are vast -- so much so that to me, spells which simply do points of damage seem a bit lazy.
3) Some spells can potentially deal damage when used cleverly in the right circumstances - for instance, a spell to manipulate fire. What's the difference between that and just allowing fireball spells? A fireball does one thing, it does it automatically regardless of almost any other circumstances, and the only real limitation on it is that you don't want to catch you friends in the area of effect. Other than that consideration, you just say, "I cast fireball!" and boom, 1d6 damage per caster level in a 20' radius, any time, anywhere.
Contrast this with a manipulate fire spell. Let's say that this spell allows the mage to cause fire to spread by x amount per round in whatever direction the caster desires, provided that there is fuel for it to burn, and also to make it explode, throwing burning embers over all within the radius of the burst. How much damage and how big the burst is depends on how big the source flame is.
You can't just break down the door and incinerate the orcs at will, unless they're gathered around a sizeable fire. However, if they have a torch, or you have an ally with a lit flask of oil ready to throw, you might be able to pull it off. You might also have to take a few rounds to spread a small fire into a bigger fire to make a bigger burst. Either way, this spell is going to be a lot more effective in a room full of straw than in a bare stone chamber.
At once, you have a spell that is more versatile -- it could conceivably be used for non-combat purposes -- and requires certain circumstances and time to be optimally useful in combat. In a way, it's like the thief's backstab ability - only situationally useful, but still quite worthwhile in those situations. It encourages the player of a magic-user not merely to throw the biggest damage spell at the enemy, but to think creatively within the parameters of immediate circumstances and resource management. It doesn't just give you what you want; you have to figure out how to get the result you want from it. Not simply, "Boom! Fireball!" but, "How can I most effectively weaponize my manipulate fire spell?"
I'm not trying to tell anyone that they're having fun wrong if they love their magic missiles and fireballs. Games with magic-users as heavy artillery can be a lot of fun, but I think a game in which magic is less about shredding bodies and more about guile and subtlety would be a lot of fun too, and in no way would a magic-user in such a game be useless or helpless simply because he can't nuke opponents for 1d6 damage per level.