Mike Mearls recently posted on his blog about issues of game balance, primarily in relation to 4e but also in relation to post-core 2e D&D. I just want to pull one small piece of that out to comment on here. He said:
If you do like combat, though, then game balance is very important. A DM needs the system to provide some framework for building encounters, or at least judging their difficulty. If each class has wildly different combat abilities and the game doesn't account for that, the system falls apart and the DM's judgment and experience have to take over. That probably means lots of trial, lots of error, and hopefully a patient enough group that a DM learns to balance the game using his own set of metrics. Of course, if a few PCs die and classes rotate in and out of the group, the balance act starts all over again.
There's some part of me that recoils at using the term "paradigm" when it comes to gaming, but in this case I think it fits. In earlier editions of D&D classes do have wildly different combat abilities. The default assumption is that different archtypes are better at different tasks, and it is absolutely assumed that combat will mostly be the job of fighter types and clerics secondarily. One of the things that is interesting about this quote is how the burden of balancing combat is entirely on the DM. There certainly are guidelines in earlier editions for balancing encounters, but this is relatively a loose balancing effort (since it is based mostly on raw HD and encounter numbers without much in the way of considering monster special abilities) and a lot of the time the players have to make the right choices and have a strategy because taking on a combat head-to-head will often result in character deaths. In later editions, or "new-school" D&D it is the burden of the DM to balance an encounter in a way that a party of multiple classes yet of equal fighting ability can attack head-to-head and have a reasonable chance of success.
The old-school approach can weather a fuzzy game balance issue because the duty is nearly as much on the players to decide what they can handle, when to fight, and when to run. Another interesting thing is how "DM judgment" seems to be mentioned as a bad thing to have to employ, as if the DM needs a concise formula for crafting encounters. Again, I think this illustrates a difference between new-school D&D and old-school D&D, but of course in older editions of D&D it is within the context of game balance being present but a fairly loose thing. As far as D&D is concerned it is a relatively new philosophy that "balance" means equal class abilities. In the past, balance was only approximate and across archetypes while acknowledging different class capabilities. This left room for player innovation in play. In the old-school there is a definite feeling that anything around the corner of the next dungeon hallway could spell doom, and thus style of play takes that into account by being cautious, asking lots of questions about the environment and what is seen, etc.
I'm not implying any sort of value judgment to this analysis, and the only reason I found it noteworthy to discuss was because it struck me as to how alien post-2e D&D is to me, especially 4th edition. For example, in old-school D&D if you choose to play a magic-user there are a host of weaknesses you enroll in, that you agree to undertake, which means you will have to adopt a certain play style that is different from fighters in the group. Not everyone liked to play magic-users because of their weaknesses, which is why multiclassing is probably so popular, but nonetheless when you choose to play a class that is not a fighter you find fun in the way that class is played. You may not get to stab at orcs in from of the line but you'll be doing other things to try to help the party when your spells run out. It's just a different mentality about how to "have fun" when playing the game. On some level I can appreciate the desire to have all characters be able to take about the same damage and deal about the same damage, and participate in the game in the same ways, but to me this new-school approach to characters takes a big chunk of the fun out of trying a different class that comes with different strategies to survival. But then old-school D&D is very much a game of adventure and survival, whereas new-school is in some ways superheroic, so there is more than just a paradigm of balance at issue here, there is an entire shift of genre.