I keep coming back to my black set as so far, I haven’t seen anyone with anything like it. (Obviously now I’m putting it up there for the world to see so I may find some others running around with it!)
I liked the leggings and I was going to go for the Black Dragonscale Breastplate but I just didn’t think that the legs went with it and it was a bit too covered up considering the ass out status of the legs.
I found the chest by having a look through a transmog site and thought that it was going to be perfect. I then decided on the shoulders and had to purposefully run it on normal to get the right colourway. Finally I needed the bow, again it was discovered on a transmog listing site. I have to say I did not grind for this, I did find it on the AH and it was pretty cheap compared to the prices i have seen it go for recently!

Helm: Thelwater’s Steelwoven Eyepatch. Reward from completing the Stockade dungeon quest to kill Hogger. Horde ca get it by killing all of the bosses in here.
Shoulders: Yaungol Slayer’s Spaulders. Normal version of this as the others are ashy coloured. Should be able to buy this with gold now as long as you have the right rep.
Chest: Double Link Tunic. BoE blue dropped for lvl 30. Check out the AH as it’s going to be easier than grinding mobs!
Back: None! Ass out and all that…
Hands: Savage Gladiator Grips. High Justice Grimstone in the Ring of Law in Blackrock Depths drops this, he’s quite near the entrance so you don’t have a huge run to try your luck at them.
Waist: Belt of the Betrayed. Thorim fight in Ulduar. Need RNJesus with you on this one and you have a fair old run as you need to get to the main building for a crack at it. But! A dark belt of any type will do or you can leave it out and let the waistband of your pants do the talking. I included it to try and add a bit of a variation on the black due to the chest and shoulders not being as dark as the hands and boots.
Legs: Savage Gladiators Leggings. Or Ebonhold Leggings. Blackrock Depths and the Ring of Law near the entrance for the Galdiator ones or any lvl 50~ vanilla dungeon for the Ebonhold ones. The Ebonhold are BoE so you can check the AH for these and the boots while you’re at it while the Gladiator ones you are competing with the drop for the gloves also.
Feet: Ebonhold Boots. Drop frmo Vanilla lvl 50~ dungeons. There are other black type boots out there if you’re struggling to get hold of these.
Bow: Astral Light Bow. Drop from Wrath dungeons. I picked mine up from the AH for a few gold but I have seen the price of these go up into the thousands! Keep looking if RNJesus isn’t looking favourably on you…

Don’t forget there are more transmog/slutmog that can be found here.