I can add some general info to the video thread but yes there is already a ranked thread...

IMO the easiest is Gun'Drak - was my first Heroic, I've always found it to be easiest, plus it has 5 badges, and you can even skip a big chunk of trash if you want. I can do this instance in ~25 min max (maybe 20 with trash skipping) and for 5 badges that makes it the best to farm IMO.

Aside from that DTK is pretty easy minus novos (but once you get him down hes pretty easy too) and goes very fast. UK is fairly easy but takes way too long for only 3 badges. Culling of Strat is pretty easy too if you're not going for any speed records.

Hardest is Halls of Stone, for sure - I mean its really not even worth trying unless you care about achievements. Oculus just requires too many mods and setup time to be worth it (unless you really care about achievements).

Middle of the road (either due to group makeup or learning curve) are VH, UP, HoL.

Once you get geared, IMO the best farming loop is Gundrak, DTK, CoS - if you can managed timed thats 14 badges in probably 1 1/2 hours. You could then hearth back to Dalaran and run VH for another 3 badges in 20 minutes.

I'll update some info in the Video thread with a rating on a scale of 10 for my particular group makeup for each dungeon