Hmm yes i figured as much by googling various topics that dealt with integration woes. Mostly the case was that the user had not properly unpacked the drivers (there were ati.ex_ and ati.dl_ files present). Thats not the case with me however as i take the drivers from live system's FileRepository folder (C:\Windows\System32\DriverStore\FileRepository) and everything is properly unpacked already. Best i figured was that the inf-s had some extra dependecies that i was not able to satisfy by integration.
I guess sysprep or setupcomplete are maybe options to get amd drivers working before arriving at the desktop?
Btw subsequent integrations showed success with DISM but im still at the process of evaluating if the driver actually installs during installation (i rather prefer to use the $WinPEDriver$ method in unnatend.xml so i dont have to bloat install.wim with drivers that quickly go out of date).