Excuse my jump in, But being a level designer and coming from source i find the unreal CSG block tool really slow when doing a level and worse when trying to do a multilevel map, i agree with that UE4 is geared more towards meshes and that the best looking levels are made using 3d model programs but my work flow as a level designer is 1. sketch a rough picture on paper 2. block out the map to get a game play feel 3. set up scripted sequences and action settings 4. detail out the map and do the lighting, using source i can block out a map in 1 or 2 hours doing 2 or 3 run around in it to tweak it out, trying to do the same thing in UE4 would take 4 or more hours to archive which is very unproductive when with UE4 you also have to create and BP or code in the game sequences, as for use a 3d modeling program to to the design i cant see me using 3dMax let say just to block out a level before finally detailing it, so to sum things up yes the CSG UE4 tools need improving even if the base csg level isn’t used in the final game produced