Absolutely agree. I have a Retribution, but only because it had the most bad-ass looks and I didn't think to magnetise it at the time. I would certainly be taking an Emperor or Oberon instead.
To use the 60cm range, you have to go abeam, where the other battleships outgun it 40WBe (Emp), 34WBe(Ob) and 24WBe(Apoc) to 21(Ret).
If you use it as a line breaker and have enemies either side, it is again outgunned by the other battleships 46WBe(Emp&Ob), 42WBe(Apoc) to 33WBe(Ret). Even if you argue that the Carriers have to stay on RO whilst the Ret can go Lock On, the Apoc still obliterates it.
Finally, with enemies all round, the Ret finally gets a miniscule edge compared to the Carriers with 46.5WBe compared to 46WBe, the Apoc still obliterates it with 55WBe, AND doesn't have to worry about the choice between RO and Lock On.
And as the Apoc still has a 6+ Prow, the only argument in favour of a Retribution is its low cost and 5cm speed.
Bugger that. Give us FP18.