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.
Any idea if they fixed this issue for Tahiti GPUs?
I remember Epoch #1 or so hashed at like 28MH/s with the R9 280X. Would be benefitial if they fixed it for that GPU also.
Same with the Pitcairn, Epoch #1 hashed at like 20MH/s with the R9 270X.
With the driver fix, if r9 280 issue is indeed the same as Polaris then a driver hack would be sufficient if AMD does not do it. I do not expect AMD to give a fix for the r7 or r9 series. AMD will only fix Polaris cause they are still selling it as rx 580.