Doom 3 patches were meant to be used for things that are better done when making a map, which are cables, maybe rails, round’ish architectural elements. None of the organic surfaces were made with patches in Doom 3, because sculpted, decimated and baked terrain will always beat patches/displacement (well, I am guessing it’s up to the skills of the creator in either case).
If someone has no clue about 3D apps, but very proficient with Hammer and its displacement tool, then by all means that’s the obvious choice. If someone is like me, proficient with 3D app, but not with Hammer and its tools, then it’s better to just stick to your guns and do layout in Trenchbroom/Radiant or even Hammer, but sculpt everything organic.
So if someone doesn’t know Hammer at all, and planning on staying with UE4, might as well just spend time learning UE4 tools and 3D app, as in the future Epic might just roll out better CSG / mapping tools and time spent learning something obsolete will be a waste.
Just my 20c 