Now, what drops frequently, right, it´s oil, so what do I see there:
In my experience, high TT oils (heart oil, brain oil and so on) drops from mobs with higher health - which also are more expensive to hunt (for instance more fapping).
As for animal oil residue, I don't think I've gotten a global of it since VU 8.9 or something(*); I think the globals of it practically was removed at the time ammo came into loot. And stacking up on that kinds of oils if what you have on your PED card comes immediately from your IRL CC isn't feasible. Just to get a grip of it, you could go to Twin Peaks and check how many street traders who buy things like thyroid or eye oil.
Personally, I haven't hunted those mobs for profit, but rather sometimes stacked up on the looted gazzurdite and caldorite to craft one or two oreamps. When it comes to iron from argos, I guess that there are one or two argo hunters out there who has used their iron from argos to skill metallurgy (=basic screws). A couple of years ago I used the iron with purchased belkar (and self-mined melchi I guess) to craft Jester D-1, looting one mineral for it sort of made an incentive to look for other minerals and do a few clicks on the "tt-bp" to create a weapon my myself.
Just from my own perspective, I think what has changed hunting patterns more is the change in robot spawns (=less drones, warriors, troopers and more "hard-boiled" robots (=drokas, legionaires) meaning I've hunted robots less, and on the other hand for argonauts the missions probably have made people hunting them more - at least until they finished the chain or possibly will hunt them way less after the change if new rules will make the iron missions less attractive).
Another recent change is the way robots (drones) aggro - they now stop pretty far from the hunter, making them harder to hunt (especially in a high mob density area). A special case is Drone Elites, which now stops at a distance you can't even hit them with an LR-6x.
Another small thing is that there currently is a lack of attractive events for smaller mobs. Last year, there were regulary events (free even) on small longu and argonauts (both small and mid-size) - right now the majority of events seems to be on tougher mobs like atrox and estophyls. Less normal fort events, more odd closed fort events that goes on for hours ran by same people each time (0 tickets left).
I can just compare with another mob tha's been changed until it was destroyed as popular "markup" mob: Molisks. The market value of teeth was pretty stable, at around 500%-600%. Molisks who had loot always dropped 4 teeth, except the higher level maturities (6 teeth for leader for instance). Then the teeth drop was changed so it was more random, and pretty often no teeth at all. After that came the regen change, which removed molisks as a good mob to recommend to newer people who asked for a mob to hunt that dropped "nice loot" (in terms of markup).
If the change of loots had come say 4 years ago, this change would have been devastating. But right now I guess since vu 10 there has been other changes that has made a bigger impact. Maybe more people will start to miss iron when the mission chains run out in august.
For drones to become popular, besides gazz, you'd need a place like vu 9 East-of-jason. Maybe generally think once or twice for the new aggro algoritm - maybe let drones come closer (say stop at 15m away rather than 50m away to make them easier to loot).
For argonauts to become popular (besides from mission grinding), regular hunting events - letting them drop iron can make good things in other parts of economy (demand for other minerals in crafting). (Personally, I don't like their change, but I'm generally conservative lol. I think they should look more intelligent and get their pants back.)
(This is just some random thoughts. I got the feeling other people, those who go explicitly for drones/argonauts and do so even with the vu 10 spawns, have a much stronger feeling for the dropped stones.)
(*) Thinking of it, I might have gotten globals with animal oil residue, but not in hunting but in crafting (components using animal oils).