EverQuest. EverQuest raiding was vastly different than WoW raiding and can be seen somewhat in the design of Molten Core which was made by a lot of EQ developers as I understand it, where you didn't need all 40 people on the ball or with great gear to clear the encounters (this is just what I've heard, I only started in WoW just before BC came out and so my progression raiding in WoW started with Karazhan, which I love as an entry raid for a host of reasons).
EQ didn't have raid cap sizes for a long time, and when first implemented I believe it was....72? 60? I can't quite recall, it was just during Planes of Power - the 4th major expansion. There wasn't a "raid UI" system in place, period. People just formed numbers of groups, one of the groups would get the credit for the kill (most damage of all parties), and then the guild would work out loot since the corpse would become lootable by anyone like..5 minutes later or something like that. Yes, ninja looting was a very real thing as a result.
In EQ with loot not being tied to instances and instead tied to world spawns entirely, your raid force could be 30 people or 80 people, all depending on how comfortable they were with each other and how often loot would be available. It was self governing; it had to be. An extra person who was literally not causing wipes or trains was an asset, whether they did half the damage of your top DPS or not. If they were cool with the raid system your guild had in place, then it was cool. If you were a cleric and could hit a Complete Heal macro every 20 seconds, you were an asset. If you were a level...uh...was it 55? Mighta been....anyway, lt's say 55+ Mage you were an asset for Call of the Hero, let alone summoning Mod Rods and dropping them on the ground all fight.
To put this in perspective, we had someone who only played a cleric who was a long running joke. You could duck in EQ by pressing D, it'd interrupt any spellcasting and prevent you from casting spells. She was screaming in guild chat for 10 minutes in a fight about not being able to heal at all. Everyone told her she was ducking. Press D. She couldn't do it for around 10 minutes of that 30 minute fight.
She was an asset.
One guild on our server raided with 80-100+ people and had a "Gratz Brabak" system where every upgrade, no matter how big or how small to their main tank, went to him before anyone else. My guild didn't do that, we spread loot around based on a complex bidding system based off DKP. Very different approaches. We both were very successful at around the same progression level doing this. We were also known for having multiple people playing 2-5 characters at once, multibox style. We'd play each others' characters if a friend couldn't be there for a raid. You were still effective playing 3+ people easily.
Don't get me wrong, skilled players were great and all, but the hardest raiding in EQ did not require your raid force to be great. It needed a few people who knew how to spawn/pull stuff and to set up the basic strategy, then a bunch of worker ants....or a smaller total number of highly skilled players that could do more on the fly than overwhelm with attrition.
I raided Vex Thal for a long time on my Wizard knowing very little about the zone and playing Golden Sun 50% of the time. I was one of the strongest wizards in the guild at that time. Same with NToV.
Hell, I raided in Velious with my guild before I was LEVEL CAPPED and all I could contribute were tiny lure nukes. It was no big deal if I died, but me being there made the boss die slightly faster. I was therefore an asset, albeit a small one at the time.
I don't mean to detract from the rest of your post (honestly I have a lot I could say when it comes to experiences managing progression raiding from WoW), but early MMO raiding was a different beast than what WoW went towards with hard modes in WotLK and even before then with BC. The shift towards raid caps allows for much more finely tuned and interesting encounters, but also puts more emphasis on a minimal skill level for players - not that this is good or bad inherently, it's just an observation. This might be best evidenced by one of our longest running members from EQ who re-founded the same guild on WoW eventually having to retire playing as his skill level wasn't high enough for the harder modes they started introducing that we wished to progress towards. Was unfortunate to see him just slowly withdraw out of knowing that he couldn't cut it anymore, and stopped raiding altogether. He was about 50 at the time I believe and represented so much of what our guild was about, personality-wise.