That can be a good thing though for thematics. The raiding society probably shouldn't be duking it out with hegemonic battleships or at least not for long.
So being better suited to raiding supply lines and the like with a capital built for that purpose almost seems fitting.
But then whats the incentive to get the alastair instead of the macnamara king or lyons all of which can go toe to toe with their class equivalents and maybe even higher. The mines are an interesting gimic but not for a ship so flux dependant as alastair. The osmond can utilize this due to it being quite fast and placing those mines is both easier and more suited to the ship. The alastair has a siege cannon and those mines... well the mines will either do very little or nothing at all due to them being so easily destroyed by point defense, and the siege cannon shell gets destroyed 90% of the time and when it hits its just ok.
Macnamara for example is the quintessential gunship/flanker type. Get rapid firing weapons for shields and armor with some anti engine missiles and this ship will both outrun and outgun anything it comes across. With proper manuevering you can run laps around the bigger capitals and shred them to bits over time.
The lyons is a durable assault platform. the siege cannon albeit underwhelming feels more suited to the lyons. it also has magnetic plating, high armor and quite decent hull, plus 2 fighter slots. The lyons is both durable and dificult to attack adding long range weapons and whatever mods you can to further increase that and a couple lyons will tear anything apart before they even know what hit them.
The king is the berserker, add heavy hitting weapons with anti shield missiles (the emp sabot missiles for example) and it will absolutely decimat anything on the oposite end with or without using its omniloader skill.
Even the hawke has more uses since its an allrounder with free drones, want a missile ship sure, LR support sure, close range brawler, well there are better options but yes technically it can, hell you can make it full blown support with nav support and ecm support due to the generous OP the hawke gets.
With all these ships that have their uses and being as effective as they are theres little to no reason to get the alastair. There are simply more and better options.