Many of the first tier of city zones can be low manned easily. I'd start with those and see how you do. Depending on your job and skill, some can probably be soloed or duoed but there's little advantage in pushing to do it with less since you all get your own reward box(which will never have anything worthwhile in it) and the more people, the easier it is to get procs.
And yeah, VNM is stuff like farruca fly and shoggoth, though on a technicality, they are all voidwalker mobs but it is confusing since they are different styles of mobs.