Oh yeah, re-importing may take a lot longer with high poly meshes. I don’t know why though.
This is almost definitely time spent cache optimizing our index buffer that is used to render the mesh. If you split up your mesh into smaller pieces (you can end up with the same poly count but just separate pieces) you should not have this problem. We’ll continue to look at ways to make this process more efficient.
Another couple of things:
Triangulating before export may help with your import time. The FBX sdk will triangulate the mesh and that seems to be really slow. Tools such as Maya or Max have much more efficient triangulation algorithms.
If you are compiling the engine yourself, you would not want to run the editor in debug and/or attached to the debugger during your production work. That is many many times slower than if you compiled and ran a development version of the editor.
Also, we are going to look at this optimizing step closer and try to make it more efficient. It is possible your particular mesh has another issue because it is very tiny. It could be getting stuck computing adjacency for tangents and normals. If you are willing to provide your mesh for us to test with it would help out a great deal.