First, about penalty based casting:
Penalty based casting doesn't work in D&D as it does in Shadowrun for the reasons Frank mentioned, as well as the following:
Buff based casting is based around the combat expertise and pwoer attack premise. That is you're trading skill in one area of combat for power in another. So you boost initiatve by lowering your accuracy, or increase your damage at the cost of your HP. This works in Shadowrun since you don't have fighter classes and wizard classes, everyone has relatively close stats. But simply trading out attack for damage or AC for hit points just won't do what we want buffs to do, and that's to make wizards and clerics able to fight better. Right now, wizards and clerics are at a decided disadvantage to fighter types when they don't use any buffs. So buffs have to create some tangible bonus above and beyond the penalties. When that's true, then you can find a way to buff everything, since by definition the benefits have to outweigh the penalties.
Iaimeki at [unixtime wrote:1163981457[/unixtime]]
This is actually what D&D does, and it fails, badly. D&D calls it "number of encounters per day," and it has so many problems it's hard to summarize them all. One is the rope trick/teleport nonsense, which is a metagaming contest between the DM and the players: the DM, to keep in line with the system's notion of balance, has to make sure they have the right number of encounters in the day, but players have a strong incentive to do everything they can to avoid encounters, because it makes them stronger. (Much, much stronger, in the case of casters.) Subsidiary to this you create tension when the players have different incentives in the system. (This is also known as the "fighter rests when the cleric says rest" problem.) Another is lack of pacing variation: DMs can't plot games with many fewer or many more than the "correct" number of encounters, because then game balance breaks down. Another is the absence of tolerance for differences in gaming styles, since again, the balance breaks down if you don't have the Goldilocks amount of combat. Another is that certain sensible effects, like Persistent Spell, can't be balanced easily if at all because they break the rules on encounters per day; so you can't add them. (Or if you disregard that and do anyways like D&D has, you destroy balance.)
Systems that rely on knowing the number of attacks you make are brittle. D&D is really a perfect example of why and how.
Yeah, this is the very reason I think it's a good idea to try to move away from the classical "slots per day" garbage and evolve into a system that balances buffing via paying combat actions, the same cost that balances out firing arrows or throwing fireballs. When the only balancing factor is the cost of the spell slot, then you only encourage people to rest after every battle, because if you can rest after every battle, the effective cost for buffing is zero. To prevent PCs from resting with spells like teleport and rope trick, the only way you do that is with a gentleman's agreement. Otherwise, it becomes in their best interests to rest after every battle.
Buffs aren't balanced right now. They can't be under the current paradigm, because the paradigm itself is flawed.
In some way, we need to add something arbitrary to the system. Yes, I know this seems to offend people's sense of fairness, but it is absolutely necessary. Because this isn't a strategy game, and while it's real easy to balance codified buff rules in a structured setting like D&D miniatures, an RPG just is not that structured. And whether people are resting after every battle, or prebuffing outside the monster's door, PCs can always find a way to beat your codified system in an open ended RPG world.
You have a couple choices and both of them involve arbitrary things.
Combat Durations: This is the system I've been preaching for most of the thread. Buffs are balanced by having to use a combat action for them. The arbitary part comes in the DM actively preventing people from getting away with prebuffing before combat starts.
No Reloads: This is a variant to slot based buffing, where the cost is a spell slot. To make this one work, you have to prevent PCs from being able to run to the ammo crate after each battle after firing off all their bullets. The only way you do this is by making spell slot recharge arbitrary. That is, you only get your slots back after each adventure. And yes, adventure is a totally arbitrary unit of measure that the DM is going to decide.
Now, I definitely think combat duration is a better idea, because it's far less abusive than the latter and balances NPCs as well as PCs. The problem with any slot based casting method is that NPCs can always cast with reckless abandon since firing off all their bullets doesn't affect them one bit. So in my opinion, you're much better off trying to balance the game on the premise of combat actions, because it treats PCs and NPCs the same.