I always liked T5 best for Rogue... hell, for half the classes. Priest, Warrior, Mage, Shaman, Warlock, love all those sets.
Hunter and Druid T5 weren't bad, just not anything great. I even kind of liked Paladin's T5, it was nice and simple and just looked pleasant enough... provided your character is female. If you were male, well, at least it wasn't as bad the ol' Orc Male in a Mooncloth Robe like from classic or Warlock T2.5 (which also looked decent on females and hilarious on males)
While T12 looks like it's turning out better than some of the past sets so far, they need to go back to class themes and not environmental ones. I'd accept just being able to dye shit though. If I could just be one proper color scheme I'd always be pleased enough.