I did a reeeeaaaly old Kev Adams ogre/troll and it was a little of a "turd polishing" exercise, that's a little harsh tbh but the sculpting was very rough indeed. Same deal with the ancient "great goblins/gnolls" that I have. Rough diamonds, incredible character but primitive from a technical standpoint.
I think there's a point with the Perrys (1984) where you see a sudden acceleration in the quality of their sculpts. No idea what caused it, but it may have been contact with Tom Meier or just a honing of their craft. The great goblins/gnolls illustrate this really well. If you look at the ones released in 1984, they're streets ahead of the earlier ones. One or two are still quite rough and based on the earlier versions, but (e.g.) the shaman, the long-eared one bottom right, the one with the mace and shield and the top-left one with the spear are so much better; I don't think there's been a better GW goblin shaman since.

The C20 trolls are from 1984, so they're in the sweet spot. The Aly Morrison trolls that followed them are nice, but I don't think Hobol and his kin have been bettered. Oddly enough, I often find Kev Adams' miniatures much harder to paint than their Perry predecessors. I think there's more finicky detail (wrinkles and the like) that can play havoc with highlighting.
I'd echo Duncan's call for some insight into the painting of this tremendous troll! There are so many tremendous and imaginative touches - from the veins to the eyes to the moss on the hammer. Astonishing!