I'd never looked at Carnwenhan as a DD weapon, Mandau seemed like it had so many more redeeming qualities over it paired with Exenterator. I think it would probably come down to what you're fighting, though. I haven't done any official testing between the two WSs, but the more I've been using it lately, Mordant Rime actually hits some pretty high numbers, occasionally spiking a lot higher than Exenterator, but not consistently. It never did anything impressive on higher level mobs from what I've done though, Exenterator always has it beat. But then again I don't have a 30% DMG boost from Carnwenhan. :P
Af3+2 hands/feet would be better if you were capping fstr.
Pieces that might have potential:
str+5 dagger skill +5 ring.
Going along with both comments, Dawnsoul Ring looks like a pretty good option over Rajas after capping fSTR.
I also remember discussing Mordant Rime builds awhile back and Cuchulain's Belt was the best option, but this was before Wanion Belt came out, so I'm not entirely sure how it compares to that. I'm also curious about Delta Earring but I'm almost pretty sure Ghillie Earring +1 has it beat.
Besides that your build looked pretty solid, not sure about the neck, Love Torque seemed like a more attractive option than sea gorget but idk.