Here is a list of loot by slot that I made when looking through the loot tables. Kind of a BiS list, although I included a few options for some slots. From what I've read, the spirit pieces are BiS since mana regen is important for progression. But if you're never running out of mana, the non-spirit options are obviously better. If someone wants to copy/paste this list with wowhead links, that would be cool, but I'm too lazy for that.
Neck - Champion's Medallion (Kargath) if spirit needed, Odyssian Choker (Twins) if not
Back - Cloak of Searing Shadows (Ko'ragh), or Force Nova Cloak (Imperator) if spirit needed
Trinket - Quiescent Runestone (Imperator), Shards of Nothing (Twins), Emblem of Caustic Healing (Ko'ragh) if healing needed, Mark of Rapid Replication (Imperator) worst due to versatility
Weapon - Spire of Tectus (Tectus). the one-hander is bad. Staff of the Grand Imperator (Imperator) is less well optimized, but okay
Ring - Ring of Infinite Accretion (Tectus), spirit so healer ring, haste. Signit of Crystalline barrage (Tectus) if no spirit needed; Golden-tongued Seal (twins) alternate spirit ring, but mastery is worse.