The size and layout of these areas aren't represented well in-game, so either way we've only get generalities to work with. The sheer number of towns and cities within the purview of Stormwind seems to outstrip Lordaeron by a fair margin, though; which is why I infer that it's the larger of the major Human population centers. With the rumors of the plague and the troubles following the Second War many Lordaeronians either migrated or returned to Stormwind as well, further increasing its population (as was shown in "Before the Storm").
Hearthglen has the look of a garrison town more than a population center, although that's speculation on my part. Either way it's not mentioned as a major city in the same way Andorhal and Strathholme are portrayed. As for Stormwind's losses, they've been involved in every conflict since the Third War. The Forsaken were victims of the War but didn't fight in it, and they didn't take majority parts in most of the other conflicts since (for reasons mostly unknown). Stormwind has involved itself in nearly all of them, and has suffered as a result.
Handled another way it's quite possible it wouldn't have been an issue, but Sylvanas did not opt to handle it in that way and so here we all are. I would wager this is an outgrowth of Sylvanas' general MO of seeing people as disposable tools for her ends - it can be very difficult to empathize or sympathize when your outlook on people presupposes that they're simply tools to be used and then thrown aside. Sylvanas fails to understand the nature of her key piece in this particular game of Chess with the Alliance, and she loses it in short order and is forced to pursue another strategy to push the game back in her favor.
You certainly can moralize selectively - much of the history of real-world atrocity is actually based on just that. I don't disagree that it's nonsensical and hypocritical, not to mention disingenuous, but it most certainly occurs.
Segregation of gameplay and story once more, really. The writers are already up front about this being a story about the Horde determining what it is supposed to be, so "word of god" in this case lends itself to the view that the Horde story is about introspection and possible revolution/reform to some degree. Island Expeditions are largely divorced from the narrative, more or less side content with a loosely connected and makeshift goal. Battle of Dazar'alor is about an Alliance assault on your would-be allies the Zandalari, with the need to respond in kind in order to preserve and further cultivate the relationship. Warfronts are direct Alliance vs. Horde battles, so posturing and jingoism are to be more or less expected on all sides. Desperation and grim perseverance sort of inform jingoism in any case, so this isn't really outside the set of expectations either.
I won't argue that the developers have done some waffling as concerns intent toward production, as they certainly have. But most of this has been a more or less behind the scenes shuffling of plot points. I mean, we still see memes about the "Purge Squad" and "Human Potential" being bandied about despite the fact that both of these points have been rendered non-canon at this point by virtue of never escaping the PTR. I would theorize that much of your view is still being colored by elements like this that have fallen by the wayside or were never fully realized - you are casting speculation from the expansion you wanted (or perhaps didn't want), not the expansion we're currently playing.