My post on Sunday generated an interesting question from AfN about encounter design. Part of my assumption when writing the post was that focus fire is the default strategy when in a fight and I feel like that should be unpacked to some extent. In a real fight focusing fire isn't really a thing because people get injured and that reduces their fighting capability substantially. When I get punched, shot, or Fireballed in such a way that I don't die I am still going to run slower, have worse aim, and panic. If a realistic implementation of injury were put into place in a fighting game focus fire would definitely take a back set to simply injuring as many enemies as possible.
However, a fighting model that takes injury into account is full of pitfalls. World of Darkness uses this idea and in that system it is a major issue because fights become routs almost immediately. Anyone who strikes a lucky early blow cripples their opponent's ability to fight back and as such encounters are often all but over by the time everyone has had even a single turn. This doesn't make a bad experience necessarily but it makes for a crappy tactical game. It also has the problem that when a character gets injured they don't get to respond effectively and many people get frustrated by this. Getting hurt is bad enough, I think, without tossing on top the issue that you now suck at everything. Of course DnD, Heroes By Trade, and many other fantasy games do not have this feature and everyone fights at full capacity until they keel over unconscious or dead. Unrealistic for sure, but I think it is more fun in a heroic fighting game than an injury based model.
AfN suggested a different sort of model to eliminate the need for focus fire too, one where if you were not attacked in the previous round you are much more powerful during your turn. Perhaps you get an extra action, become more accurate, do more damage, whatever. This is certainly a good way to reward combatants for spreading their attacks out and trying to engage all enemy targets but it also suffers from a few issues. First off it requires keeping track of another state for every combatant and secondly it (much like the injury model above) penalizes people for being attacked. Anyone who is a melee combatant or who tries to tank for other characters is never going to get to take advantage of the bonus for not being attacked and I don't particularly like a system where the people taking the greatest risks are penalized further.
Another similar option I considered was a model where combatants could choose to avoid an attack by giving up their next action. Obviously this could not be a guaranteed thing or no one would ever get hurt but it could mitigate the blow in some fashion. I think this sort of system would lead to fights that lasted forever though as people tossed away their turns to defend themselves. The solution I am still most comfortable with is one where combatants have decent options to defend themselves that they choose to use. If someone is being focus fired they can use the basic Defend action or they can use a Power that makes them hard to hurt in some fashion. Focus firing is still a good default plan but intelligent opponents will use their abilities to reduce its effectiveness. For HBT this seems like the best option to me.