Sorry if I missed a post along this topic (I looked!)
In most games, the strategy of having all/most units attack a single unit is usually rewarded by the game mechanics. This is because the unit usually deals out max damage until it is destroyed, so it make sense to eliminate the opposing forces as quickly as possible, which is usually one by one.
Personally, I think this is somewhat silly and is not as much fun as it could be. I would much prefer to see 2 units or small groups duking it out in the context of a much larger fight.
The end result I would like, given all other factors are equal is this:
A group of units attacking a single enemy unit will lose to a group that is attacking all different enemy units.
So, what game mechanics can be implemented to reward spreading out your attacks as opposed to concentrating fire?
As an example, I think Sins of the Solar Empire tried to reduce this by having shield mitigation, or something like that...basically the unit took less damage by percentage based on the rate of enemy fire or damage, or something like that. (Ok, I admit that I didn't really understand it)
Here is my one suggestion to help this:
Units that are not being attacked deal out 2x damage over time. This could be from each attack doing more damage, or the unit making more attacks. This makes sense, if a unit is not being attacked, then it can really devote its attention to offense.
So, does anyone else agree with the premise? If so, what are some other mechanics?