Hello (hope this is in the right area...), I'm making my first 3D design for Dota 2 that I started on yesterday, a staff for Kotl, but I'm currently having issues with importing it properly. I downloaded the base model off of the Valve website and tried both the .fbx and maya files with both my custom model and the default…
You probably missed skinning some specific vertices on your mesh to the skeleton, but at the same time, the files from the workshop website are sometimes bugged, so you may have to extract them from the in-game files.