I don't know, even getting to hit all fighters within an arc Ships top out at 2 dice, with most only having 1.

Ought cap ships be that effective against starfighters? I seem to remember a handful of X-wings destroying a Death Star...

Lancers and dedicated anti-squadron ships could be better sure but fighters seem to regularly approach capital ships, especially Rebel starfighters.

It isn't a binary solution set, caps vs fighters, because while technically both are capital ships the abilities and roles of large caps vs small caps are very different. Large cap ships like SDs will be very inefficient when dealing with fighters, getting 2 or 3 attacks (at best) against fighter squadrons for each shot, a total of 2-3 dice or so. However, smaller cap ships will be able to match that damage with a much smaller point investment, making them much better. So a CR-90 will be very efficient as a fighter screen when faced with massed fighters, where the Assault Frigate will not. If we went a full 300 points of fighters, I would expect it to easily burn down an opposing fleet filled with large caps but would likely evaporate in one or two rounds against half a dozen CR-90s regardless of what else was in that list.

Fighters will be very good at bringing down the largest ships, who are good at bringing down small capital ships, who are in turn good at bringing down fighters. Add the screening rules, and you have a balanced design that incorporates Rock Paper Scissors elements without turning it into a RPS list building game. Each piece will have a specific role, and using ships within their roles (and forcing your opponent out of theirs) will be one of the keys to winning the game.