And there is no real requirement for it to do this. The 'official' warship designations are and always have been almost completely meaningless for babylon 5 capships.
Despite the battleship tag, there is therefore nothing inherantly wrong with the Octurian-class being a close-range brawler, nor with it being a ship designed to dominate multiple smaller opponents rather than beat down the one big one. The problem is that as described, it is the Primus-class Battlecruiser's bigger brother in basically every way.
Since it offers no real difference to the battle-priority ship, it's difficult to justify taking one Octurian over two Primus with better speed, better net firepower, the same total fighter wing, and since there are no active defences, better toughness.
A 24" range battle laser would be fair enough, but then one has the obvious question of why the Primus gets the short end of the stick...it's a simple fix but then provokes demands for another. Plus the whole point of the re-thinking of the centauri fleet is to stop them being dependant on beams as a primary armament! Finally, doing so repeats the issue (to a lesser degree) one priority level up; the Adira-class is such a standout ship from the rest of the fleet at least in part due to those long-ranged Drakh neutron cannons.
(Question to the playtesters: Why exactly is the sullust armed with such a long-ranged (by Centauri standards) main gun?)
I like the suggestion of replacing the beam and matter cannons with plasma accelerators (although with a range boost). There's no problem with using interceptable weapons as a main ship-killer; if everyone must have a non-interceptible primary weapon then interceptors themselves become next to pointless.