So just out of curiosity because its not mentioned here but you have tried with the DitherTemporalAA? I remember when we worked on Dead Island2 at my old company we heavily used those features and were pretty satisfied with the results. Also, Epics new hair rendering heavily depends on dithering and TAA to make things work.
Just ignore what I wrote if you already tried that 
Just wanted to make sure since masked material + TAA only doesnt yield usable results^^
Cheers!