yeah I've tested with the firestrike stress test and got 99.7% and not had any issues in games. I'm using vega 64 bios and card has an EK full cover block on it. Checking max temps lastnight with gpuz after playing PUBG for about 1 hour Core was 43c and HBM and hotspot both 50c.
HMB at 1100mhz and core boost was between 1615 and 1625mhz
My testing suggests that HBM2 overclocking is critically dependent on the quality of the cooling. I can clock the HBM2 up to 1060MHz under air cooling providing the core clock rates are kept low enough to control the temperatures under load. However, gradually raising the core clock rates either causes instability or wipes out the benefits of raising the HBM2 clock above 960MHz.
I would be interested to know how much performance benefit you see raising HBM2 from say 1000MHz to 1100MHz when using a water block.