Have you checked the thread for the best settings? Maybe that will help?
My testing was purely by eye - I manually cached an area of my city (which is a photogrammetry city) and compared low, medium and high. High really is the only way to go, but it takes 249572 years to grab any decent amount of area. Low was a complete joke.
The LOD was terrible at release and got better after patch 1. Frankly, they have a ways to go in general, and unless you can find a fix here it may be a bit of a waiting game. You could disable the rolling cache too - maybe it’s slow?