well have your flashed modded bios to your cards?
my rx570 from asus with modded bios and with these clocks 1165 core / 1950 memory can make around 900h/s in cryptonight
which is almost 2 times less then vega can push
while mining eth with these setting the card is giving 29 mh/s, so your number a little low. so maybe you have to flash the modded bios?