In terms of battleship shielding, with a large-planted bomber, you need to hit every SN as soon as the energy recharges in order to have a hope of dropping the shield...and that's only the first time 'round.
Not to mention that that battleship is spewing out thousands of DPS at speeds of up to 2k m/s. 2 bombers will have a chance against a poor battleship captan, to really kill a decent one, you need 3.
As for GBs, the simple fact is that a bomber cannot refire fast enough to drop the shield, then hit hull, assuming the GB pilot knows the slightest thing about what he's doing (I can hold off a single bomber in a GB...).
And we all know that cruisers in this version are not worth the investment...