Here's a quick BIS list that I made.
If you're going for 4 piece (which I recommend...and which is in red below), then the best offpiece to take will be the Gauntlets.
Slot
Item
Boss
Helm Helmet of Guiding Light Kromag Neck Feldspars Control Chocker Blast Furnace Shoulders Pauldrons of Guiding Light Operator Thogar Cloak Barrage Dodger Cloak Oregorger Chest Battleplate of Guiding Light Flamebender Ka'graz Bracers Fleshmelter Bracer Blast Furnace Gauntlets Gauntlets of Dramatic Blows Hans'gar and Franzok Belt Uktars Belt of Chiming Rings Iron Maidens Pants Legplates of Guiding Light Blast Furnace Boots Iron Bellow Sabatons Operator Thogar Ring1 Firemenders Smoldering Signet Operator Thogar Ring2 Spellbound Runic Band of Infinite Preservations Legendary Trinket1 Ironspike Chew Toy Beastlord Darmac Trinket2 Auto Repairing Autoclave Blackhand Weapon Fang of the Earth Kromog Offhand Heart of the Clefthoof Beastlord Darmac
Other options
Slot
Item
Boss
Neck (no spirit) Gruuls Lip Ring Gruul Cloak (no spirit) Runefrenzy Greatcloak Kromog Throughput Trinket Goren Soul Repository Oregorger Gloves Gauntlets of Guiding Light Iron Maidens
Also, here's a very nice drop list:http://i.imgur.com/MDnpGMj.png