I was getting serious tanking of FPS, from 72 to mostly 22-25 but some areas down to the teens.
Did a bunch of playing around with various settings. Finally got it down to shadow distance. Every area that tanked hard, every single one, just putting shadow distance to medium flicked everything up to 72fps(144hz screen with v-sync maxing out at half).
Hit low preset because medium locks out some choices without you knowing. IE if you hit medium preset then set god rays to off in advance.... they stay on, because it's retarded. Hit low preset then anything you change in advance sticks.
I played with every freaking setting till I found that in certain areas high shadow distance was killing it. From what I've seen as well, ultra shadows look good, medium shadows look good, high looks crap. It goes really blurry and soft. Medium looks like marginally lower quality than ultra, high looks like entirely different shading style that frankly sucks.
High shadow distance my 5820k had no thread more than maybe 50% but my GPU was dropping from 90% usage to 35-40% usage and sub 25fps in certain areas.