Nils has an interesting post up about MMO combat systems. As he notes, many systems have a simple optimal strategy that reduce to using a certain skill rotation, or to using certain skills whenever they become available. My response was that I'd like skills to be more situational and require judgment in their use.
When I say skills should be "situational," I mean that whether or not to use the skill should be an interesting decision without a consistently provable right answer. For example, a skill that can be used only after a critical hit is not situational if the best strategy is use it whenever it's available. That's just a simple reaction and not an interesting choice. So let's take a look at some examples of ways skills can present players with interesting decisions.
Resource management. Many MMOs give players a resource (like mana) that powers their skills. Common practice these days is for the resource to regenerate quickly to avoid downtime. If resources regenerated more slowly, then players might have to choose carefully which skills to use.
One great example of this is Vanguard's druid class. The druid is basically a traditional mana-based caster with an unusual twist. In addition to his normal mana-based spells, he has a set of powerful skills called "phenomena" that draw from a limited pool of "phenomenon points." Phenomenon points are similar to mana except that they regenerate much more slowly (I think it took something like half an hour for my pool to regenerate fully). That presents druids with interesting choices about when to use their limited supply of phenomenon points. Do I want to do massive burst damage quickly at the cost of all my points? Or do I want to save some for an emergency heal I might need later? At the same time, it avoids the downtime problem by making mana regenerate fairly quickly.
Reactive skills. By this I mean reacting to what the opponent is doing or what's happening on the battlefield. For example, a spell interrupt with a cooldown is reactive because it requires the player to watch what the opponent is doing and use the skill at the right time.
The Vanguard druid has a nice twist on this as well with its counterspells. One counter has a long cooldown but can reflect a skill back at the opponent. So if a monster is about to hit you with a massive damage spell, you can reflect it back in its face. The cooldown is fairly long, so the player has an interesting choice about when to use it. Should I reflect that damage spell? Or should I wait for the self-heal I think is coming?
Skills with drawbacks. Less commonly, some MMOs include skills with powerful effects but huge drawbacks that have to be taken into account. For example, the "Absorb Pain" spell from City of Heroes is a healing spell with a twist. It's powerful and cheap, but in addition to healing the target, it damages the caster and makes the caster unable to be healed for the next 20 seconds. When used properly, it massively increases healing output and saves power, but when used carelessly it can easily cause the caster's death. Whether to use it is a matter of judgment without an easy answer.
Offense vs. Defense. Many strategy games involve choices between offensive moves and defensive moves. In chess, you have to decide whether to spend time protecting your own king or to go all out against the enemy. Rift occasionally demands these types of choices; for example, if I get mobbed by enemies while soloing I need to decide whether to spend time healing myself or whether to try to kill one of the mobs quickly to reduce the incoming damage. However, MMOs typically don't offer this type of choice as often as they should. Soloing is usually so easy that the best strategy is unrelenting offense, and group combat usually assigns each player an offensive role or defense role, so no choice is required.
So what do you think? Are there other ways MMO combat systems can give players more interesting decisions to make?