Blender does have hierarchy, though it's a little harder to use than Trueview.
Anyways, I don't know if that technique will get rid of the disconnected geometry problems DOGA produces - I kinda doubt it.
To fix most of the DOGA problems in Blender, just import the model in as a DXF, select all and then scale it down to fit the grid. Then, making sure you ONLY have the parts of the model selected (ie, not the default camera and light as well) press crtl+j to merge them all into one object.
From there you can just tab into edit mode, select all verts and press W > remove doubles. As far as I can tell, this will stabilise the mesh to the point where you can begin working on its textures or mesh editing etc, though you'll probably need to clean up some bad geometry in a lot of the parts before it's all solid.
Edit: Err, yeah - basically what Water just said in more detail.