Honestly I'm always a few levels ahead of where I am in the story. Last night I jumped from 36 to nearly 39 in like an hour or so doing the main quests, they give you ridiculous amounts of EXP.

Instances are for farming Materials for your gear, not leveling, just do your quests and your dailies and you should be fine, it's the most straight forward part of the game yet somehow people don't grasp it.

As a bonus, * doing A and S bounties only to maximize the EXP you get from your 10 bounty limit.