Deathcom3s: Ah yeah, at the moment there is no easy way to do it, there is a third party program for Source called DispGen (by a awesome guy called Cannonfodder) here is a link that explains it more:
https://developer.valvesoftware.com/wiki/DispGen
You also need to have a Source 2007 SDK (or similar) installed, like the CS:GO editor or the TF2 editor,
After exporting the heightmap to vmf with DispGen, you open it in a version of Source Hammer (I tried to open the VMF directly in Dota2 Hammer, but it seems that the exported vmf version was not possible to import),
Once the vmf has been re-saved it can be opened in Dota2 Hammer,
You can also use a program like Vue and export heightfield into fbx or similar and import it directly,
One good thing by open the heightfield in Source Hammer is that its pretty easy to do adjustments in the displacement (smooth out areas etc)
Hopefully this will help, otherwise just msg me on Steam :)