I do like these community packs but I do agree with @Norseman & @Mark_Turner on their points. I'm fairly new to mixing and when I first started DIYing, it was with a One Shot; I felt more comfortable with it, knowing the flavoring %'s were correct in a single bottle; add PG, VG, & NIC, and I'm done.
Also, even if I were to buy a One Shot, and I didn't like it then at least I only bought that one and not a bunch of flavors that I probably wouldn't use in another mix (which is also a probability). One shots also helped me to take the leap into buying individual flavorings as well, so I could make more of the product if I did like it. One shots are are a win win.