On topic. I'm also at 68ish and I was having the same debate. I've leveled by instancing since 35, and I was thinking about shaking things up and actually questing; doing NS for consortium rep. (5 bags of gems every month!) However, I think I'll stick to dungeon crawling. At 68 you can start doing Shadow Labs, Sethekk Halls, Shattered Halls and Steamvaults. These will all take you to exalted in their respective repuation, plus there is a shot at getting primal nethers, and pre-raid equipment.

If you're running with rested exp, at this point, just level in dungeons. If you quest you won't really capitalize on having the rested exp as much as grinding on mobs. Most quests can be done with less characters, so I do quests while i'm bored at work since my setup at work isn't able to tackle 5 copies of wow. Questing gives decent gold at 70. Questing before your rep is appropriately topped off (aka consortium rep before honored) is not as efficient as questing once you've capped rep with dungeon runs. So if you're consortium rep isn't honored from running mana tombs, then I wouldn't do Netherstorm.