These drivers must work better for Vega, though I was not able to install them for Vega FE. For Polaris I don't see any changes in speed for ZEC.
Unfortunately, I have no idea what you mean, I don't have enough experience in these Linux problems. I test my miners on ubuntu 16.04 and gpu-pro drivers, for old cards I use 15.12 drivers and Ubuntu 12.04, for NVidia I use Ubuntu 14.04 with CUDA8-compatible drivers, it works fine. Since you did not specify any details, may be you use some different Linux or drivers. My miners are for Windows mainly, I compile them for Linux because of a lot of users requests, I don't test all Linux builds and drivers because it can take forever.
Sorry, I will give you more info.
I lack experience with theses new drivers too but I think I could help you troubleshoot it. Moreover, I think it is an issue you will have to fix in the future if it's on Claymore side (could be some change they made on amdpu that requires intervention from user side, no idea...)
So I use the free amdgpu driver and amd-staging-4.12 kernel. I will check if I have the same issue with linux-mainline (the linux 4.12 you find in your usual distros).
I didn't have this issue with amd-mainline-hybrid-4.11 kernel.
So my guess it that they changed some code between amd-mainline-hybrid-4.11 and amd-staging-4.12 kernels and that it will be merged sooner or later in the linux mainline kernel and in the gpu-pro driver.
Here's the AMD kernels I'm talking about :
https://cgit.freedesktop.org/~agd5f/linux/Thanks for the linux support by the way
Edit :
No issue on linux-mainline either, so I guess the code has not been merged there either.
So the issue only happen on amd-staging-4.11 and amd-staging-4.12 kernels which are the kernels/drivers where the code is first merged so people can use it before it finally lands in linux-mainline (which can take quite some time).