I just remember leveling in late Wrath and just steamrolling content. I had no heirlooms, but none of the bosses in any of the dungeons were like they were when I played in Vanilla. I don't think leveling in dungeons was a waste of time at all. That was the game. End game raiding was there when you reached max level, but getting to 60 was part of the journey, the game. I loved Deadmines. I loved Scholomance. Heck, I loved just killing mobs in Western Plaguelands, with no quest associated with my indiscriminate ghoul-slaying. It was fun!