Do you usually only see performance reduction when you scope into a forested area? Or even while using the eye focus zoom in the same scenario?
I get a huge performance dip when I do this, and I've figured it's caused by the anti-aliasing on the trees.
No matter what setting I have it on, I get massive FPS loss zooming into a forest, whether through a scope or the eye focus zoom.
It only happens when zooming in, never looking normally. Only fix is turning anti-aliasing off completely.
I guess AA is just a huge hit with that many trees. Still odd it only happens on zoom, It's almost like they're loading the highest LOD possible even if they are still super far in the distance.