I don't think a story should strictly have to tell us what is and isn't normal for trolls, though, when it can show us. It's a pretty fundamental pillar of good storytelling; when we're being introduced to a new world, we should be able to take it on good faith that the things we're being shown are being shown to us for a reason. It's the same logic that tells us most trolls have black hair and red horns because the 12 we've seen all look like that, even though 12 is such a mathematically small slice of the population! (I also like to think of it as Dave's Conjoined Twin logic - even if the story never tells us EXPLICITLY that Dave won't have a second face on his stomach if he ever lifts up his shirt, we can be pretty confident that's the case because we trust the story to tell us the things that are relevant and avoid telling us things that aren't relevant.)

As far as the brooding caverns go, I don't know that I would take Vriska and Tavros' recollections at 100% face value... I mean, Tavros is being asked to recall a traumatic event that would have supposedly happened when he was literally a baby - I'm not surprised he doesn't remember if it happened or not! Meanwhile Vriska has a very vested interest in claiming to have experienced something, if it makes her seem like a more idealised, battle-hardened troll. So I could easily believe that all the trolls either did or did not enter the caverns. Though I dispute your reasoning for Karkat: didn't his ancestors breed a lusus just for him, specifically so that he would have something to protect him in the caverns - and he wouldn't have to be adopted and taken away from normal society like the Signless was?

I hope I don't seem like I'm picking on you by also talking about the drone thing HAHA I'm just very interested in talking about this topic (and I wanna bump the thread back up to see more people's responses!): it's not like the drones in a real life beehive are, like, under the queen bee's mind control, right? They have the same amount of autonomy as any other bee in the swarm. So I don't find it particularly strange that troll drones serve the same entity every other troll ultimately serves (though in the end they DO serve essentially the same purpose as a drone in a real insect colony, since their primary function [at least as far as the comic is concerned] is delivering genetic material to the mother grub). Really the more interesting aspect of this line of questioning to me is just how conscious the drones really are... do they actually just have one-track bug brains compared to the more humanoid members of their race, or are they fully functioning people who happen to be forced into servitude by the same machine implants that give them their rocket boots and missile wrists? ("drone" works so well specifically because it's a double entendre that refers to both a robotic weapon and a type of insect, btw!) I like to think it's a little somewhere in the middle, where they trade off some of their brainpower for their massive hulking bodies, but there's also absolutely a glimmer of humanity stamped out early on by a rigorous training and conditioning program, reinforced throughout their lives by cybernetic upgrades.

Anyway, as fascinated as I am by the drones in particular I'll be productive and add something new of my own LOL: there's a line in Hiveswap Act 1 about how eating eggs with bad parasites in them would disrupt the good parasites inside a troll's guts, and spinning off from that I like to think that most of the inside of a troll is parasites. just like how lots of the human body is composed of technically foreign microorganisms, but scaled way up: if you cut open a troll's body you'd find that a lot of their organs are actually worms and insects working together to keep the body running. I also imagine that if you cut open a piece of troll (bio)technology, it would look quite similar!!