I think Claymore did a wonderful job on this one.
At first i did get a decrease from 165Mh to 140-ish with dual ETH-DCR.
Then i played with it and got back up. Seems like the software is becoming more and more advanced, thus "needy"
These settings worked for me:
EthDcrMiner64.exe -epool eu1.ethermine.org:4444 -ewal 0x3ba6Bec13899d67c4B9c37230bCd49dB822A6b35.minerx -epsw x -dpool stratum+tcp://decred.eu.nicehash.com:3354 -dwal 36PoLAKNUiYdUz22BuKDxBorSp2j1C7G9H.minerx -dpsw x -esm 1 -mode 0 -tt 70 -asm 0

Running 6x RX470 OCd
core voltage -30mv Core 1100MHz Mem clock 1950MHz (Using MSI Afterburner)