DevFee pool job has very high difficulty
I use XMRig on a rig with 6x GTX 1060 3GB, hashing at 2730 H/s on CN-R algo. 
The devfee pool sends jobs at 1000xxx diff. I'm sure that you get no accepted shares at this huge diff in that short time that stays connected.
You should set a fix diff for devfee, according to miner's hashrate. HRx10 or HRx15 it's a very good choice.