Finally I can test and confirm that AMD has fixed the issue with slowdown at high DAG epochs for Vega/Polaris/Fiji cards. They are going to release new drivers in a few days.
When new drivers come out, will it work if i just copy OpenCL DLLs into miner folder?
I don't think so, the changes at the driver level.
Did AMD provide you with both Windows/Linux fixed drivers or just windows?
I test everything in Windows 7/10 currently, I don't have any info about new Linux drivers.
Within 24 hours I will release new version with Vega support and fan/overclock management for 17.7.2 drivers, for Windows. I will release Linux version a bit later.