At any rate, if you manage a difficulty 10 exotic weapon, lone fighters and other small ships will be scared of getting close enough to be "Power word: Scrunch"-ed by a dedicated spellframe/weapon for "Scrunch", this on top of potentially Kanna laughing her ass off and dumping the whole ship's battery into a single shot spell to ruin someone's day.
A Difficulty 10 weapon would likely be threatening even to cruisers, actually. Especially at first when no enemy shield operators know they need to defend against "Power word: Scrunch".
Basically: Skal autocannons or a D6 weapon if you want to drive off enemy fighters, annoy corvettes. D8 weapon if you want to drive off corvettes and swarms of fighters. D10 weapon if you want to pose a credible threat to a Real Warship (TM). Just be aware that the super-disproportionate punch of D8 and D10 weapons has a limit of "until the enemy figures out and implements a magical countermeasure to whateverthefuck".
(The fact that exotic magical attacks are defendable-against in theory if you know to expect them is part of why Chelskan fleet and army doctrine goes for More Dakka, No More Than That, with an option for "haha no magic for you" on a strategic scale- Who wants their expensive Rust Monster wunderwaffe to become useless once the enemy defends against it? At most, at that point, it becomes an extra burden on their preparations and attention, not the I Win button such projects are hoped to be.)