This post started out as a reply to Chris’ comment in the Age of Empires Online post he put together, but was fairly tangential and soon took on a life of it’s own.
I’d divide new content offerings into three categories: creative content, streamlining features, and new abilities – which would include using new units, playing new civs, etc.
The first category, creative content. To take an example from Dragon Age: Origins, the Leliana’s Song DLC is new creative content. What’s offered is the chance to see new areas, follow a new story, possibly get some different fights which provide a unique challenge. In an RTS game, this most obvious example of this would be a new map-pack, such as the Historic Battles DLC for Halo Wars. The most common complaints about this sort of content are that it’s “too short” or “too expensive.” Personally, I have a soft spot for this sort of content. It’s tangential to the core game – you never find yourself playing the game and suddenly thinking “If only I’d bought that extension, what I’m doing right now would be more enjoyable.” In strategy games, it allows for an unusual set of challenges which can add fresh life to a game growing stale; in story-based games, it lets developers flesh out details of their story and game universe which couldn’t reasonably be fit into the main game for one reason or another.
The second category, streamlining content. To stick with the DA:O examples, the Party Storage Chest available from the Warden’s Keep DLC is an example of streamlining content. It allows you to more easily organize your inventory, and keep track of items you want to hold on to without worrying about overfilling your inventory or accidentally selling something you want to hold on to. This sort of content is fairly game-specific. A hypothetical strategy game example of something like this would be if a game offered a purchasable premium match-making service which helped you quickly get into skirmishes against people of similar skill. Personally, I tend to be irritated by this sort of content. If there is a real gameplay issue and it can be conveniently addressed by developers, that’s something that should be done by a patch rather than a niggardly pay-to-fix system. If it’s not actually a real gameplay issue then I could care less whether this content exists, but I’m certainly not paying for it. I admit there are certain gameplay issues which it would be too costly to address in a patch but which still would be nice to have fixed. However, these tend to be the sort of sweeping changes you see in expansion packs or sequels, and the reason is simple: they’re expensive. They’d have to charge so much to release it as DLC that they might as well go the whole nine yards and make a full-fledged expansion.
The third category, new abilities (and I use the term “abilities” loosely). The Stone Prisoner DLC for DA:O is a good example of this; the new civilizations you can buy for Civilization 5 are a good example of this sort of content for a strategy game. In any sort of competitive game, this is a road to disaster, and the reason is fairly simple: balancing. A really easy way for a developer to make a quick buck is to simply release a bit of overpowered content and watch as thousands rush to buy it so they can win without the need to invest time and develop actual skill at the game. Naturally, if you want to sustain this system that means that your next offering must be even more powerful, and so forth. Those who are not interested in forking over cash for regular upgrades end up out in the cold.
But suppose you’re a good-hearted developer (or simply one taking a long-term view) who is trying to make all his new offerings balanced with the existing game. The simple fact is that you don’t have as much time to play-test DLC as you do to play-test a full game, so the new DLC is unlikely to be as well-balanced. Even if you somehow do just as well with new content as you did with the core game, you’ll have outliers (just like you did in the core game). Some DLC may be too weak, which means it’s unlikely to sell well. Some of it will be too strong, which means it’s going to fly off the shelves as soon as people realize what a mistake you made. At this point you have three choices. First, you can nerf it. This is what you would do if you had released something like this in the core game, but because people just started spending money to buy specifically this feature you’re opening yourself up for a shitstorm of complaints if you nerf your offering to rebalance things. Second, you can ignore it and keep trying to keep everything else at the old game balance. The result of this choice is that you’ve got a noob cannon on the loose. Pretty soon your game is filling up with people who only play that class or faction, and players start hosting games which explicitly prohibit choosing that faction, and things go downhill from there as you continue to make mistakes and create other over-powered choices. Ok, so say you don’t nerf your mistake and you don’t ignore it either. Your third option is to try and re-balance the rest of the game to match the new balance accidentally imposed. This means your future content releases are going to be “overpowered” by old terms as well, so those who are simply buying no new content are quickly left in the dust. And further, sooner or later even your new balance will be broken by another mistake, which means it’s not simply a one-time upgrade but a continuing investment for players simply to stay competitive. This is pretty much the path taken by expansion-funded MMORPGs and by collectible card games, and while it doesn’t mean those games are never fun it does mean they tend to end up costing unpredictably large amounts.
PS: Not all new content need necessarily fall into one and only one of these categories; this division is for conceptual purposes. In fact, full expansion packs are expected to offer quite a bit from each of these categories.