Ravenholdt rep grind.

[Ferocity]

Without Shen'dralar. Insane is comparable to Explorer

For me, Shen'dralar was the easiest rep from The Insane actually. You could combine it with goblins' rep grind quite efficiently, and could also make some nice income. While DMF pre-dailies was just a plain gold sink and Ravenhold is just pinnacle of tediousness and boredom (pickpocket couple thousands mobs with all the limitations on bag space and pitiful amount of valuables in those junkboxes).

[Earrl]

I leveled a rogue to farm lockboxes for my achievement character. got sick of buying them. Farmed the heck out of LBRS for quite a while. some people say there are other places to go farm, but I preferred LBRS.. no competition, no unwanted world PVP, and a lot of mobs in close vicinity. Do it enough times and you'll figure out a good pattern to go through the dungeon as well.

[Deleted]

To be honest I can see where the people with Shen'dralar rep are coming from.

Bloodsail Buccaneers: Plant +15% rep banner, camp Shakes O'Breen and his buddies =>3k+ rep per hour
Darkmoon Faire: Daily quest farm, turn in all the tokens => halfway done
Steamwheedle Cartel: Kill pirates in Tanaris/Barrens
Ravenholdt: Kill mobs to 11999/12000 and then farm lockboxes on rogue alt.

Sounds pretty damn easy to me. Still, too lazy to do Ravenholdt and DMF atm >.<'

[etethave]

I did start working on Shendralar. Did DM runs till I got enough librams then knocked off what mats I needed for it.

[Tekloth]

Rogues have it even easier since 4.3. I'll quote myself from Wowhead;

With the upcoming legendary quest chain for rogues, you, as a rogue, can get 3150 reputation from the quests without any reputation bonuses, and 3465 reputation with the rank 2 guild award bonus. Plus if you're a human that amount increases a bit, but I don't remember how the 2 rep bonuses are modeled (do they stack or is 1 calculated after the other or what) so I'm not gonna dive into that. Someone with better knowlege could calculate the bonuses from being a human as well.

Takes a few lockboxes off the tedious grind

Provided that you've killed enough mobs to reach 11999/12000 rep with Ravenholdt.

[jahasafrat]

As far as which option is less time-consuming, I'd say grind the mobs for as long as they give rep before turning in boxes. From my own experience with Ravenholdt, that is definately faster than doing turn-ins from the beginning.