Just got out of a match with a balanced space marine fleet, against 7-8 Dominator cruisers. Got hit by about 10 laser accurate Nova shots before I could close minimum distance and by then all but my Battlebarge was destroyed, and of course Dominators are also very strong at close range with their macro broadsides.
Never stood a chance...
Seems currently it only takes about 4-5 hits to destroy a strike cruiser, which seems like a lot, but when you can bring that many Novas and they have such a short cd its really not much at all. And even if it took twice as many shots, rolling in with half health strike cruisers against a bunch of dominators would be an instant lose anyway.
Seeing as Novas have been a balancing problem since the beginning of game 1 I figured I would throw in my two cents on balancing options.
Make Nova Cannons Weaker... I actually like that Nova cannons are strong right now, so although this would work, I feel it would make them far less enjoyable.
Make Nova Cannons Less Accurate... I would really rather not go back to the wildly inaccurate shotgun novas of game 1.
Longer Cooldown... Lowers overall damage potential in a given game, but doesn't remove the main problem which is in my opinion their ludicrous alpha strike potential.
More expensive(like 2x)... This seems like a potential winner to me, the Novas can remain the powerful long range weapon of mass destruction they are supposed to be in the lore, but by making ships that mount them much more expensive it means you can't stack 7-8 of them in one game. Also a lack of ships means that high alpha damage is a must for Nova Cannon fleets simply to be on par with your opponent once fleets clash.
Ineffective against shields?... As a more creative option you could make it so that Novas do dramatically less damage against shielded targets. This would require Novas to be combined with other offensive options, even just some escorts, in order to soften up the targets before unleashing a volley. It would help slower fleets to not be rofl stomped by massed volleys from across the map, and fleets without shields like eldar and necrons have maneuvers and stealth abilties that allow them to evade Novas effectively as it is.