Cataclysm is very linear, in that if you miss one quest you're stuck and unable to progress quite frequently.
It is a major flaw, in the quest design.
But if you want to experience the full "lore", doing almost everything gets you the experience.

I've only leveled two of my teams through the content.
Partially because those teams were for PvP and are quite fun to play... as soon as they were level capped.
And partially because of the linear nature of Cata.



Instances and PvP are both options for experience.
Not sure how good the experience is, compared to quest stacking.
But any instance run you do, or BG your team gets honor from, is bonus experience that you no longer need to earn from quests.