I've reached 15.758 MH with overclocking and undervolting with ease and no problem.
I've a rx560 Hynix too, which timingstraps/clocks do you use to get 15.8MH? I can't reach 15
I'd like to know that also I bought a few gigabyte rev1 rx 560 when it was impossible to buy a 570/580 well for a normal price, but I'll have to say the rx 560 isn't a bad little card