The Elite Four themselves are poorly, although not as "lol, Surf/Psychic/BoltBeam Starmie sweeps them all at once" like the Kanto Elite Four.
-Aaron could have done better with his Heracross. Drapion is an interesting curveball, and his use of Vespiquen I approve.
-What's up with the evil evil DT Quagsire Bertha's packing?! Hippowdon was a major annoyance with its massive HP.
-Flint's team, lack of Fire-type notwithstanding, is pretty meh. He needs more klutz-trickeroo Lopunny and a better Infernape moveset.
-Lucian had a pretty interesting but lacking team. At least the Mime and Bronzong combo was quite a 1-2 whammy.
Cynthia's team - Spiritomb has No Weak, Garchomp is a fast and painful sweeper, Milotic is as tank as ever. If she had better movesets and held items, she would have made many people RAGE over the difficulty - How about a Round 2 Team for her in the inevitable Crystal counterpart to round out the Gen4 Triangle, gamefreak?
(BTW, anyone can sweep all 5 of these high-level ingame trainers without breaking a sweat with L80s, but that's a given.)