Which algorithm are you mining ?
What are your GPU settings ?
I am sure someone with Vii cards can help you.
Lot of people use SRBMiner + VII without problems.
algorithm CN haven
voltage 981 mV
core clock 1649 Mhz
mem clock 1100 Mhz
its about 2600 h/s each card cryptonight haven
power consumption 130 watt in adrenalin drivers log