After watching the "Hot and Loud" video, I went to better test my "workaround" for Black-Screen. I simply disabled gpu core P7, also in PPT memP1 matched Hynix memory timings table to 800mhz. (625 does not exist in the table)
I noticed some artefacts in Heaven even with max voltages in P7 (tried 1225mV after unlock), so I´ve figured my issues were not from core. But SoC /mem-controller voltage island. GPU uses power from just the pciEx.
by setting memP2 voltage to 1075mV (increased from 850 vbios default), i fixed the vdroop and artefacts.
Maybe the long term increased you suggested is better achieved with a memP2 25mV increase by year...