The ability to combine static mesh is rather important for a jungle setting, where a single mesh is repeatedly used. This reduces draw calls substantially. Last I heard, you couldn't combine mesh's in RO2 SDK, was this changed? I tried to combine a couple of identical mesh, and they just vanished, although the pivot widget remained, and the new combined mesh existed in the scene list. Maybe I did it wrong? Going through the stock maps, I see this technique is used heavily for the tree's.