If you are going squadron heavy, the Yarvis is worth getting as well.
Otherwise, Nebulon B's lack a real role in the rebel fleet. Jousting is not the way to win. Yes, a Nebulon B gets one turn at long range where it is better at jousting. 3 Red dice doesn't kill anything. The next turn a Victory will eat it. If you are going for firepower it is much better to just use the assault frigate, or the CR-90
I disagree. Nebulon roll is not a jouster, it is an ass-biter. Put your fleet on a side and the Nebulon with 1-2 fighter on the other side. When opponent turn toward the rest of the fleet (because they will, else they turn their back to most of your fleet), Nebulon come take some bites of the rear of the opponent fleet.
Why not just take 2 CR-90s A's with Enhanced armament? The do a better job of it, and are more maneuverable so are more likely to actually get there.
2 CR-90 with Enhanced Armament worth 108 points instead of just 57. This is 1/3 of your fleet instead of 1/6. So it totally worth it for your opponenent to turn an upgraded VSD toward your CR-90 to protect the rear of the fleet, while turning the same VSD for a 57 Nebulon, the opponent is giving up ~50 points avantage in the main fight.