Depending on the amount of polygons per actor, that is highly usual to happen. One way is to optimize the LOD for each actor as 1st priority. If that took place already, then if you are using Displacement somewhere (landscape, actor materials) try to reduce the Tesselation Multiplier to lower numbers and give your material some awareness about the camera distance, so you can set a Tesselation Multiliper values higher for close to camera objects and lower values for the distance ones. Sometimes texture sizes affects performance, but that is really a matter of experience to set properly. Let me know if your are still aware of the tips above and need some more clues.