There were people who grinded by mobs even in Cata+ simply because it is more efficient.
When I played I completed all quests so I know what I am talking about. I completed even such hidden quests you probably never heard about, e.g., drop from rare ambush of stealthed assassins on Southshore, treasure map quest chain in Westfall, elite quests in Duskwood, one of them led to Wetlands with underwater murlocs (oh my, back then you could spend only some seconds underwater, and murlocs were many...), etc.
Though I admit, I also did dungeon quests. I also don't understand why people neglected dungeons - they gave you a lot of exp and provided nice gear upgrades. Leveling with or without dungeon gear was like playing different games.