In Progressive Lightmapper, adding LODs to Mesh Renderers drops the baking performance radically. This issue is much more pronounced with large projects that use lots of instances with LODs. The project attached to the case is relatively a mid-size project where the issue can be observed.

Steps for reproduction:
1) Download the project below
2) In `Assets/NextGen/Scenes`, find scenes called `Nuclear` and `Nuclear_noLOD`
3) Bake the scenes and observe the performance difference

Notes:
- Baking performance (mrays/sec) and CPU usage differences can be observed across the scenes
- Not a regression