I went the opposite direction. Try setting the -dcri intensity really high, not really low, with your rx 480. You might be surprised. I'm able to mine 2.5x as much dcred with only a minor loss to ETH speeds. More than makes up for the extra energy use/fee.
Thank you for a suggestion, I tried it ;] set -dcri 50, upped to 60 soon after, achieved ~1400 Mh/s for decred, but Eth went down to ~47-51Mh/s with 25W more for 2 RX 480.
What is your setup and numbers with and without second coin mining? If you would -,-