I know TR and GoW4 and many other games got gains in dx12 like they should. Next week new version of Dx12 comes out in WoW that suppose to boost performance there even more as its lacking hard atm in raids. Ill do some tests see how that does.The latest Nvidia drivers might* have improved things. To early to tell but I played 4 rounds yesterday at it seemed smoother.
Anyway DX12 isn't any Nvidia thing. Gears of War 4 does it well. So it can be done.
If blizzard can up up grade a warcraft 3 aera engine to use it properly everyone can but they are just lazy :/ looking at what 15-20% jump ??