Well i think its the potential D6 automatic hits. That can really spell doom for ships tbh. However when you look at the scatter etc it's not always soo bad.
I played the best of 3 games the other day, will need to put a report up but i have no pictures

. Perhaps i should finish adding the details to my fleet and get some pictures up... first time painting BFG ships though so not sure they are the best painted.
It was just an introductory game for us both. I used my 4 wardens as Castellans, and my 2 Protectors. I had Kor'el with a single re-roll. (He allowed me to use the CPF fan list)
He took two imperial cruisers and 4 Sword class frigates. The Cruisers were Lunar class but with the Nova Cannon upgrades. He had a standard Admiral (LD8) with 2 re-rolls (made the points pretty even)
Now when two nova cannons fired at the same target i couldn't help but notice that they started to become far more deadly weapons. Capable of easily wiping out multiple escorts in a single hit. Given the Lunars more capable broadside as well this caused some problems in all but my last game.
I think people see the D6 on a Nova Cannon and think "Can cripple a Capital ship!" I see them as more useful against squadrons where the scatter isn't as damaging and where two of them firing together (espec if ships are squadroned) can tear through escorts with ease.
This was certainly what my oponent did and it caused me no end of grief in the first and second games. When i lost Castellans pretty quickly in the second game it allowed the sword escorts to swing behind my Protectors on AHF and trap them between the Lunar class.... Only my frontal fire power allowed me to reclaim some honour so to speak. My opponent hadn't played Tau and didn't realise how fast their torpedos travelled. 12 Torps into a Lunar class followed by 2 Manta bombers really does tend to cause some worry and i got lucky with a critical roll.