And would not have rivaled the slaughter which is, again, the ship they would have weighed it against. Stop trying to use modern IN, it's not fluffy in this case.
On the contrary, SC with lances and THs and supporting WB CAN rival a Slaughter. Remember that SCs have 6+ armor so can are almost as hardy as the Slaughter. Adding lances would allow the SC to now be an efficient gun platform able to tear down the shields and plink the Slaughter for damage and the existing TH loadout of Str 2 would give the Slaughter headaches. The SC has a tighter turning radius that it could get behind the Slaughter and shoot or maintain an abeam profile. All that for cheaper points.
I'd say that the common SFD Monitor is being heavily underestimated here. +6 and two shields and turrets make a single monitor a tough nut for a SC or a nova to crack. One on one, a nova killing it is nearly impossible, and they cost within 10 points of each other.
Look at the speed and tell me the Monitor won't be outmaneuvered and killed by an SC? Esp one with lances.
It would not be the first time they did exactly that. Particularly the Minotaurs and the Space Wolves.
And they almost always come out of the deal much battered and have to use teleport attacks to mess up the opposing ship. Your point?
Torps are anti-ship weapons, having no use in planetary landing support, and by your logic, prohibited. BCs, at least for SC, are not a long range weapon, and are unsuitable for what you describe.
Torps might have no use against planetary assault but they most certainly have uses in exterminatus. IN find torps a more acceptable weapon for SM since 1. they can easily be taken out by ordnance or 2. outmaneuvered. BCs are not suitable for what I described? And why not? it's not like you need long range to hit a planet.
BCs are also powerful anti-ship weapons. A lance only inflicts a critical hit 1/6th of the time, a BC does 50% of the time. Since a critical hit represents massive internal damage to a ship...
Crits won't easily kill ships. Every lance hit after shields is a point of damage. BCs will hope it gets the right profile to get a lot of dice and crits will contribute to its destruction over the long run but the target ships can weather BC fire better than lances.
"Bombardment cannons are equally devastating in ship-to-ship combat, capable of blasting apart any capital ship in just a few salvoes." Armada, Page 21.
Sure just about any weapon in BFG can. But lances are much more efficient in doing so. Again, it's a problem with efficiency.
So, the Avenger is NOT a proper gunship, and not a 'true' threat to other ships, because it doesn't have lances, despite having a more powerful broadside then a Retribution class battleship?
Yup. Sad to say, Avenger isn't. FP16 is nice but against an abeam target greater than 15 cm, that's 5 dice. See the problem? With the Retribution, that's 4 dice and 3 lances. See the difference?