1 NC per 500 seems to be the only real balancing that needs to be done, or you make it so for every NC you have, you must have 1 cruiser (Or higher vessel) without one.
The statement below makes sense from both a game point of view and a fluff point of view.
"-Fluff dictates that to fire an NC ships have to pay particular attention to targeting, and they don't turn/perform any manouvres while firing. LO prevents turning."
Another option would be not allow it to be fired after it goes on LO. This could be used to represent the cannon being reloaded (Yes in fluff they fire giant shells, which take 40+ minutes to reload), but being fired accurately causes them to reset some controls/systems (Kind of like a rush to get the next shell out, which when firing real weapons, you can fire a rifle rapidly, or fire accurately, but never both)
Or just don't let them go on LO 2 turns in a row.
Nerfing the damage output makes zero sense fluff wise or game wise.
Besides they are really only scare to 1 or 2 other fleets, and that's chaos who loves to sit back and fire away and Necrons since they don't seem to be an in your face fleet. When you look at the other fleets, Orks, Nids, Marines, Other IN, Eldar, DE (Tau I am very unfamiliar with, so not sure where they sit), the NC is not much of an issue since you are generally within it's minimum range after 1 or 2 rounds of shooting, or they just get a save against it....unless you the fleets mentioned.
I generally only run with 2 in my fleets, and only because Dominators are a great all comers ship (I take them in every fleet I write, no matter if it's Eldar or whatever, because when he does fail his save...oh man, destroying an eldar bb with one shot is just awesome)
