This does sound low for a RX570 on Monero, I get almost 500 h/s on an R9 270x 2GB mining Cryptonote, and 750 h/s on an RX 470 4GB.
But what I found is that the R9 270x runs much better on Claymore v9.7 than it does on v11.2, so try using earlier version of Claymore and see if that helps.
I have the same card (R9 270X, but with 4GB) and haven't found v9.7 to be quicker than v11.2, the opposite in fact. So there's probably something else influencing the performance. I get 470H/s with v11.2.