One of the grindiest factions in Pandaria also has one of the best tabards: the August Celestials. A recent xmog I did with the tabard is one of my favorites:
Shoulders: Pauldrons of Surging Mana; Chest: Icy Scale Chestguard; Hands: Heroes' Earthshatter Handguards [Shaman only]; Waist: Necrogenic Belt; Legs: Black Dragonskin Breeches; Feet: Tsunami Boots; Duel-wielded Mace: Black Icicle.
ClothFor clothies, I know tabards can be hard to pair with robes,
but I found a match that looks pretty good (if I do say so myself).
Shoulders: Lunar Mantle; Chest: Frozen Shadoweave Robe; Hands: Hands of the Light [I didn't realize until too late that these were Priest-only gloves from challenge-mode dungeons];
This leather set might work best with Monk/Druid classes. For Rogues, the Tier 9 (Alliance-only) and Replica Rogue Dungeon 2 set look really good with the tabard.
Shoulders: Hide of Chromaggus; Chest: Tunic of the Dark Hour; Hands: Replica Darkmantle Gloves; Waist: Eva's Strap; Legs: Trickster's Leggings; Boots: Charged Footwear; Weapon: Ghost Iron Staff.
This xmog set was something I was going to do if I still had an axe and a fist weapon :P. For Shamans, the Tier 7 10-man set looks really good with the tabard.
Oh man, Plate-wearers. They have several different options! Warriors, you can try the Tier 9 (Alliance-only) set. Death Knights can match with the Tier 11 Normal or Tier 13 Normal set. And, Paladins would look good with the Tier 11 Normal set.
Shoulders: Pauldrons of Edward the Odd; Chest: Ornate Mithril Breastplate; Hands: Cobalt Gauntlets; Waist: Klaxxi Lash of the Doubter; Legs: Legguards of the Unseeing; Feet: Rock Furrow Boots; Weapon: Wrathful Gladiator's Slicer; Shield: Lost Pavise of the Blue Flight.