I went with the rep-grind approach with exp as a byproduct. My goal was to hit honored or higher with the major reps (which happened to coincide nicely with the pvp gear moving to rep vendors).

For instances that I couldn't clear but could kill a boss or two (mana tombs comes to mind at that level) - I would just run in and kill as much as I could then reset.

Escape from Durnholde - i found my best exp/rep per hour to be to kill up through the second boss but before you take off to tarren mills. Seemed like this was yielding about 700-800 rep and a nice little chunk of exp for about 30-45minutes of clearing.

Mana Tombs - first room + boss and reset yielded a good amount of shards and some nice exp/rep, started doing the first two shortly after.

Sethekk Halls - grind to first boss, blow all cooldowns etc to burn him down fast and reset.

Blood furnace was pretty easy for me after i over-leveled and out geared it, nice quick runs for decently good xp/rep an hour.