Who really grouping in these zones

[Rumham]

Just like post ask - who is really grouping because I enter a major zone and see ~18 people but where is the group? Looking around to the locations there is little to no group but also so many there. Is it a hidden solo or something else? Where are the actual groups ? And not just the level sixy Druid who is pulling a zone for the grip of three. Something is odd to have so many but so little and again where are they even located - I always have see invis up so for sure have not misssed any. You’ll notice it now that you read this