There's a difference between playing in good faith, and playing to design intent. You can't blame anyone for not playing in good faith, when they bought the books and spent a year of their life trying to make sense of rules that seemed to defy all logic.
For many people, 4E represented an entirely new type of game, which they'd never seen before. Previous editions all worked by process simulation. Even competitors, like Palladium Fantasy and GURPS, were much the same. How would anyone even know to treat 4E as a genre-emulation engine, if they'd never encountered one before?
Fair enough on good faith from a historical standpoint. I agree with you that the umbrella moved and WotC wasn't great about explicitly laying this out. That said, internet forums were talking about this shift and pretty much did lay it out explicitly within the first year (or less?).
The minion issue was one of many that is solved by embracing the paradigm shift/design intent shift. I'm not saying everyone should like this shift (different strokes...) but I don't like the arguments that "4e mechanics don't make sense if I come at it from angle A and I refuse to use angle B". There's some debate about whether WotC actually even knew how 4e was best used at release, as many of the staff seemed to be stuck on prior edition norms too. But it doesn't matter to me-- once you do know an interpretation of intent that makes sense then not playing the game under that umbrella is not playing with good faith.
It's like the martial healing "shouting wounds closed" debates.
"I don't think shouting should close wounds"
"HP in 4e are very abstract -- it represents a combination of luck, heroic spotlight, will, resilience, ability to avoid the killing blow, etc. Think of martial healing as trying to emulate the moment in fiction when someone is encouraged by their allies and finds a reserve of will to go on. Or here's 4 other ways to think about it..."
"Nah, I like HP as flesh points. It just doesn't make sense."
Based on everything I'd seen of the world, the dwarves should have been able to hold their own, for at least a few rounds, with the PCs as a deciding factor that let them prevail. I guess I should have stopped and explicitly asked the DM whether or not they were minions? That's not something I would ever have considered. In any other game, that would be meta-gaming.
Not knowing the full context, but this seems like a DM mistake then. 4e is nice in that it gives the DM an easy toolkit to emulate fictional tropes. If there was direct evidence that the dwarves could hold their own for a few rounds, then the DM shouldn't have made them minions.
Again, minions is not an "in world" thing. It's simply a gamist mechanic to emulate something that is true in the world, namely "these are redshirts that compared to this particular competition in tactical encounter combat are outclassed and will die with any meaningful attack".
For planning purposes you should be able to tell by the infiction evidence or by asking the DM, because characters often have better knowledge than players.
I guess you could ask "are these miners going to be treated as minions?" But it doesn't really have to be that meta. "What do I know about Drow? Will these dwarf miners stand a chance?"
Again, if your DM showed you the dwarves were more powerful earlier than she should remain consistent. But unless the characters saw these dwarves fight these particular drow then how would the characters even know how long they would last? Because miners are tough and can survive hard labor? In most genre fiction that doesn't tell you a whole lot about surviving magical attacks, sword chops, arrows, etc.