> and if that target is already being attacked they look for the next closest one.
There are certainly scenarios where a target saturation algorithm makes sense (I once wrote one to hunt down a spread-out group of fragile targets during a hackathon, for instance), but I think that's actively counterproductive here. Focusing down one target is the optimal strategy for line battles.
> Putting all defense on one ship and using it as a forward tank is a valid strategy but is risky as losing a ship is punished hard. So maybe spreading ships in a line is actually safer because it distributes damage better as enemies will attack different ships depending on their position. That is where positioning becomes important.
In practice, I'd say that around 95 percent of the damage goes onto the front ship pretty consistently, so long as there's a meaningful gap. For positioning to be of interest to the player beyond that, I think there has to be a bit more complexity.