Did you ever farm for flasks during vanilla?
Obtaining Black Lotuses was a time consuming process. It would spawn in one location in 3 areas and had a long respawn timer. Once collected you needed the Scholomance Lab to convert into flasks. Add on all the mats for potions and I would spend an easy 2-3 hours a day farming before or after raids. The alternative was to buy off the AH but gold was not exactly easy to come by either.
Twice a week we would organise two groups to farm the +20 Stamina (I think) chops from the Feralas island. Potions and food buffs all disappeared on death so progression required a lot of mats or gold especially when we were raiding 5-6 days a week.
Flying and the change in flask mats and production in TBC was a huge time reduction for raiders when compared to Vanilla. Of course, it was possible to raid without farming much but those guilds did not progress fast except in MC. Usually on reaching Nefarian, the mat /gold farming requirements jumped up exponentially.