You are asking some dangerous questions During classic there wasn't a lot of pugging going on in 40 man raids. Anyone who tells you otherwise is either an extreme minority or never play live classic and bullshiting you. In the two years I raided in classic, the only "raids" that I successfully cleared in a pug were ZG and AQ20. There were some really important reasons for this such as:
Raid lockouts - Many new players who are used to pugging don't know that back then everyone was locked to their RaidID so you were locked to the raid as soon as you entered(or killed the first boss based on the lockout system/patch). It wasn't worth it to join raid, kill one boss, get locked to that raid and come back the next day to find that the raid is cleared or have problems filling the raid again the next day because no one wants to start on 3/4th boss etc.. So everyone had raiding schedules and basically just raided with their guilds
Attunements - filling a raid with 40 people, that wanted to spontaneously raid at the same time as you, not part of even a casual raiding guild, attuned, and not saved was not an easy job even on a high pop server.
Resistance gear - there would be certain dead ends for pugs because of the lack of resistance gear, it was quite time consuming to farm them and some required epic patterns and raid drops to complete. Although some resistance gear could be solo farmed or crafted, the "good" resistance gear dropped from patterns within the raid and needed drops from the raid to craft so if you were pugging solo, it was very unlikely that you could have a good chunk of resistance gear. It was a guild effort to get the tanks decked in resistance gear then start distributing it to most active players. In the pugs you would probably have people disbanding groups when they reach a certain boss because they would know they can't get past it anyway. Then you are locked to a dead RaidID for the rest of the week.
Random requirements - I am not talking about crazy naxx40 needing multiple hit capped priests to even get the first boss of a wing or needing 6-8 tanks. Simple things like having enough number of mages who knew how to decurse on the first boss of MC, or having a hunter with tranq shot to use on the second boss, having enough locks to banish on the 4th boss.. are all going to be a hassle in a pug. For example, sure you got a hunter that got the tranq shot from the first boss and he will use it on the second boss but he had to suddenly leave the group, its a pug who cares. now you have 39 people who got locked to just 1 boss and can't continue unless they find a pug hunter who is willing to start on the second boss and has tranq shot..
Ninjaing items in smaller groups such as UBRS/Strat/scholo "happened" but it is unlikely to happen in a 40 man raid. This was before server change or name change existed so any ninjalooter got "Exiled" sooner or later and had to start a new character from lvl 1 because everyone knew his name and refused to group with him.
I hope this helps!