But the fee is only 1% for ETH-only mining mode... that's what is posted on the front page...
Yes ETH single mode is 1% dev fee. If you dual mine you will pay 2% dev fee on ETH side only. Dev fee never mines from the extra coin like dcr, sia, pasc but you pay for it in ETH mining time.
In that case it makes absolutely no sense to dual mine because the profit from the extra coins is far far less than another 1% of ETH gone.