@sknox ; Not trying to debate you, perhaps even reinforcing your second point...
Fair enough, and you're right... Orcs, demons, the bulk of armies be they good or bad, the birds from 'The Birds,' GoT's dragons, wolf-packs, zombies, Native Americans in old movies, Godzilla, etc., etc., all make for fine overwhelming forces that can threaten absolute destruction or make for a lot of chaos on carnage action without any backstory. Then again, they're not really characters, more some force to be overcome.
Using your LotR reference however, when used as more than simply a force or representation of evil, in the Hobbit all of a sudden we encounter Azog.
Not a lot of backstory, but, enough that it makes his motivations and actions have some basis in reason. It turns his random brute force into a personal hunt that implies, besides basic mindless rage, he now has calculated intent that states bluntly, 'this individual will have to be stopped for our heros to make it to the end of their quest.'
So, I agree on the one hand, yet disagree if you want the individual or group to be something more than a powerful threat.
That said, and sticking with your example; in the RPG and ultimately my writing using my barbarian culture, they always had orcs and goblins pretty much as you describe... A basic force for heroes to demonstrate their prowess upon. Bored one day, I sat down and decided to do a bit more with them generating two branches of the orc tree, Vorka-- a higher minded, formal militaristic based race who thrived on stoic honor and duty... and Mourkra, an extremely primitive, brutish, lower minded, superstitious and spiritually minded sub-species.
For each I devised a history, minor differences in physiology, culture, religion and so on... then let them sit idle.
When the day came that I needed my axial character to not only show her skills, yet personality, ability to learn, compassion, weaknesses, etc., I thrust her into an encounter with a Mourkra group. By there being more to that race other than just savage brutes, it gave me a chance to demonstrate MUCH more depth with my primary character than simply being heroic. I would 'show not tell' what she encountered... and by the end of that story (actually my last with all that), it was difficult to say who was more heroic, faithful to their gods, honorable and so on.
The mindless brutes to readers became 'individuals' that my readers could relate to or at least understand and therefor, sympathize with. BUT, most importantly, the Mourkra's depth, gave my protagonist vastly more opportunities to show her depth, flaws, growth and so on.
So, are they a simply a brute force, or something more? In my opinion, dependent upon how much you want your primary characters depth to be shown, they can be either. But, until they are more, they offer little past fodder.
K2