In 1e, 1 15th level fighter (with a normal sword and AC 1, how's that for non-Monty Hall?) against 100 goblins (ave hp/goblin is 3.5), I take the fighter every time. He hits AC 4 with no strength/magic bonuses on roll of 2 (and 1 always misses). So he drops 15 goblins per round (average damage with a sword, no str bonus, is 4.5.) -1 goblin per 20 die rolls. The goblins hit only on a natural 20. By the DMG, only 8 can attack per round meaning over 5 rounds, only 2 goblins hit. (Also, 1e had no "official" crit rules.) That causes 2d6 damage, if you give all 15 goblins he attacks a one-off whack at him (via the equivalent of a held action), say he faces 120 attacks or 6d6 damage. (120 because sometime he will not roll enough damage to drop the "average" goblin.)
I like his chances. (Of course this assumes the goblins don't attempt to use the overbearing rules.) His chances only improve if he has a Strength bonus or a magic sword. And give him 3-4 buddies, and I think the party destroys 100 goblins without breaking a sweat.
As I said above, I conflated the goblin with the orc. 100 orcs is an entirely different fight (the fighter needs AC 0 to keep the only gets hit on a 20 benefit), but only because the fighter can cut them down like chaff. Add a MU (flying of course) and a healing cleric and I still like the party's chances.
The point though is that in a dungeon, you won't find 100 anythings. And at the size of normal encounters, historically, you stop seeing goblins and orcs after around 4th level (maybe 8th level in 3e). They are no longer relevant. And that is something I liked in older editions. There's a certain cathartic reaction the party should be able to go through. Once, the sight of 6 orcs charging would strike fear in the party. Later, the sight of 6 orcs charge would cause laughter in the party. (Finding out the orcs are trolls under an illusion causes even more laughter in the DM, but that's a different catharsis.)
Actually, I was reading just the other day about a 1e module where the players couldn't go in the front entrance, because it was a low-level module and you'd encounter a few hundred guards walking in the front door. Regardless of that, not every adventure occurs in a dungeon. Are you suggesting that it's impossible for the PCs to encounter a orcish warparty of a few hundred orcs outside?
Also that "1e" encounter would go much differently in 2e. I was addressing both editions. Even in the 1e scenario, you said yourself that it would be a different story if the goblins used overbearing, or if they were orcs. Seems like you built yourself a bit of a corner-case. (I mentioned Monty Haul simply because a party dripping in magic loot would most likely have very little to fear from low HD creatures.)
My experiences must have been very different from yours, because in the good old 2e days, we encountered plenty of low HD creatures well above 4th level. If they were in small groups either it was a trick or they were admittedly laughable, but in larger groups or when partnered with a more powerful creature, they were far from negligible.
Admittedly, I think that minions are a more elegant means of handling such weaker creatures, but not everyone feels about minions the way I do, so it's good to have alternatives.
Lastly, 100 goblins (or orcs) was just a minimum. As I said, 100 goblins (or orcs) are only worth 1500 xp. That's half the price of one Spriggan Gnome (not exactly the biggest challenge for a high level party either)! Heck, it would take 400 orcs just to equal a Hatchling Blue Dragon (with regard to xp value). So you could easily toss
several hundred such critters against the party at once, without breaking the xp bank. Give them all ranged weapons, and use smart tactics (such as overbearing), and I don't think the party will be laughing for long.
My point is that in all previous editions, low level creatures could still be a threat to a high level party. 3e was the odd man out in that it accomplished it by allowing you to add class levels to these creatures, but in 1e and 2e a few hundred single HD humanoids could be quite the threat to a reasonably powered adventuring party, assuming the DM didn't just use them like Zapp Braniggan.