That wasn't what was said at all. The suggestion is to have your dorfs stay nearby instead of running all over the map after enemies.
Really he said 'stay within 3 tiles of each other when moving', this means when they are moving they stay withing 3 tiles of each other.
Sometimes enemies are so weak in comparison there's no point in them ganging up.
In DF combat? I had an iron whip from a goblin lasher go straight through my adamantine clad soldier.
And if you told someone that carp was the most deadly creature in the game they would laugh at you. DF is full of surprises.
Clearly there would be some sort of mechanism in place that would determine a general CR for enemies. That goes hand-in-hand with this sort of suggestion.
But how though? Any modder knows that there is no attack power in weapons, if you based if off of skill, a legendary hammerdwarf is still worse then a competent swordsdwarf, if you base it off of the value of weapons you'll find that people are ignoring the legendary hammergob because his fellow gob is hauling around a steal long sword.
It would help by getting a dorf that's chasing a retreating enemy to save the life of one that's being mauled.
What if you were outnumbered though, which happens in so many situations. The AI goes wonky donkeys.
Let's say you have three dwarves against four goblins. Dwarf A and B are fighting Goblins 1 and 2. Dwarf C is fighting Goblins 3 and 4.
Because of the AI dwarves A and B detect that dwarf C is outnumbered and
both of them stop fighting 1 and 2 andcharge to his rescue.
Goblin 1, 2, 3, and 4 are now all huddled around Dwarves A, B, and C. Dwarves get killed.
Even in combat your dwarves would be as smart as piano wire. Dwarves would stop attacking whoever their attacking and run over to help another dwarf. In the process getting killed themselves by the person that's chasing after them. They would prefer to go around a pond to help a dwarf then stand and fight the goblin they are currently facing. The AI would not work.
Or if you have ranged dorfs it would get them to take out their counterparts.
Once again, ignoring the melee group that storms right through the front line to kill your archers.
Again, to quote myself "Furthermore, because of the lack of variety, ambushes are oftentimes all ranged or all melee." making the AI useless except in a very unlikely situation.
Tactics are only as good as the people using them and offering players more control and variety is a frakking good idea. Especially considering the aim of the game is realism and 'attack nearest' is not always realistic.
There are tactics in the game, and offering the players more control is a very good frakking idea, and I support such an idea. But the tactics have to be good tactics. You are giving AI more credit then it's worth, it's called artificial intelligence for a reason. Plus you fail to take how much coding it would take to make such a system. Even in other games with better AI you still come across the problem of NPC's running into walls and failing to go around.
How is 'attack nearest' not realistic? Attack the first person you see. Seems realistic to me.