Battleships are like any other ship in that their use depends upon how well optimised they are for their role. For example, the Retribution is fast enough to keep up with the rest of the fleet, has an armoured nose and a strong torpedo salvo. All these attributes optimise it for a role of line-breaker. That is, charge headlong at the enemy, on AAF, shotgun torpedoes when close enough and then get inside their formation on LO. What this sort of ship would require to make this possible is strong broadsides. What it really doesn't need in order to be able to perform this function is long range broadsides. Hence the original Retribution with its weak, long range, broadsides was poo. Conversely the BFG:R Retribution is much better.
An example of a different kind of BB is the support platform. This ship is meant to hang back to the rear of the formation, abeam of the enemy and support the rest of the fleet from afar. It relies for defence on shields, hits, turrets, facing, distance and friendly escorts. It doesn't need speed, but it does need weaponry that can reliably support the fleet from a fair way away. It doesn't need off-side firepower, but rather instead focusable firepower.
The Emperor battleship is a pretty good example of this second kind of BB. It has very weak off-side direct gunnery, so not much wastage there. It has 60cm range and can bring a reasonable amount of direct fire to bear on a single target. It has prodigious AC capacity and this, combined with its guns, allows to reach out and touch the enemy quite well. It does not pay points for unnecessary things like prow armour or speed. All in all, a good ship. It would be better if it had lances instead of WBs, due to long range penalties, and it would be nice to have a stronger dorsal armament at least, but for the price, it's a good ship.
So those 2 are examples of good BBs. For examples of bad BBs we need look no further than the Oberon and Apocalypse. The Oberon was originally a clone of the Emperor (back when the Emperor was 345 pts) except that it replaced 2 launch bays each side with 2 60cm lances and cost 10 pts cheaper. This meant that, compared to the Emperor, it lost 4 AC and picked up only 2 lances (since the other 2 are off-side and ill-suited to the support role). This is a poor trade, but at least those lances don't suffer range issues and it was a bit cheaper. A decent alternative for the admiral that didn't like AC much, or usable as a fun alternative.
However, when the Emperor got its cost adjusted to 365 (ie, +20 pts), the Oberon got really shafted. Instead of having its cost increased to 355 pts, leaving it in the same comparative position as it was beforehand, the powers that be decided to instead reduce the range of its prow and dorsal weaponry to 45cm. This made it a support vessel with no range, ie, useless. Above 30cm roughly 9.5WBs are worth 2 lances. So this made the Emperor the better gunship in the 45-60cm range. This is ridiculous, given that the Oberon trades 4(!) AC in order to get that edge in firepower.
The other fail IN BB is the Apocalypse. Armoured prow, strong short-ranged broadsides and front fire arc only prow weapon makes this a line-breaker. But alas, this ship is far too slow to be usable in this role. Any canny opponent seeing an Apocalypse making straight for his lines will assuredly place a blast marker in contact so that it falls behind the rest of his fleet.
Of course, the Apocalypse does have the ability to fire at long range. With its slow speed it could be used as a support ship. However, its range is unreliable, depending as it does on a successful LO. You would, of course, be wanting to LO with your long range support gunship anyway, but the point is that should you fail the test, you would want to still be able to fire, not lose your full broadside fire simply because the enemy is too far away. Also, if you do happen to fire at a ship over 45cm away you lose 10cm from your already crappy speed. This isn't in itself bad, since you don't really want your support ships to go anywhere anyway, and most of the time the crit will be repaired before it even becomes an issue, but in a few rare instances your opponent will just have to put a BM in contact with the Apocalypse to turn it into a stationary target next turn. Support ships tend to rely upon aspect (amongst other things) for protection, and going from one of the best defensive aspects to the worst unexpectedly would really suck.
So crappy as a traditional line breaker and crappy as a traditional support ship. And to top it all off it has piss-weak dorsal guns. Well, despite all that, it's still usable, if only just. There are 2 ways to use it, one is to treat it like a large Dominator, though to get the most out of it in this role you'd need to take it in a NC fleet. It would still be better in this role if it had a BFG:R Retributions broadside and dorsal weapon load, so still not perfect.
The other way to use it is to have it come in at an angle, moving as fast as possible and locking on as she goes. This should give some broadside targets if the LO goes well as well as some targets of opportunity for the NC. In the latter stages of a game it's even possible she'll end up breaking their lines and get to fire both broadsides. Meh.
