I also think the Desecrator should be made into the Wages of Sin but without all the good stuff it gets and at a lower price.
Basing the unique ships on a actual battleship class is a good idea... logical and less room for errors. Still takes a bit of unique out of unique.
What kind of cost are we talking about? 360? 350? I think it's quite important, because the Wage of Sin is almost equipped as the Despoiler class, but would be considerably cheaper then. The Despoilers option to switch 2 launch bays to 9 torpedo tubes would also go to waste, since it would have almost the same armament as the Wage of Sin but at higher cost.
My conclusion (in case the Despoiler stays at ~400pts): Either the Desecrator gets priced around 380 pts or it should remain with 4 launch bays. The Wage of Sin can keep its 6 bays then... back to unique.
I've got the same concern about the Relictor and the Desolator. Until now, you had two possible reasons to field a Desolator. Either you wanted a really cheap battleship or you wanted a fast ship to khorne-board the enemy fleet. With that in mind you were o.k. with the lack of guns the Desolator has.
If we're going to sell the Relictor at 300pts we kill the Desolator, since the serious punch of the Relictor is much more valuable than a couple of long range lances.
Since the Desolator can't (shouldn't) get any cheaper and the Relictor mounts a capable fast&furious-package, I'd price it at 320 or 330.
/edit: Oh, right. Traitor Legion discussion... all point costs above considered without CSM.
