No, I have 18.4 installed and I grabbed the 18.4 Client download (not the experimental one). I downloaded the folder, extracted it, the cut/pasted each folder's content's into the 7 days to die Steam Folder. If it helps at all, I don't get the new quest system either, but still have the vanilla one.
I got the Darkness Falls overhaul mod and I believe I have it installed properly (though I am having an issue so that is questionable). The game loads fine, just the new quest system doesn't show and the whole upper UI is the vanilla version. Any ideas?