I don't think it was too high, I personally enjoyed the challenge and coming up with an effective strategy to beat them. Strategy played a huge role in defeating the Elite Four, in this case, I think it was more important than having pokemon at levels stronger than all of the Elite Four and then just using whatever moves are the strongest (though that's what you mostly have to do against Cynthia's spiritomb, though you have to keep in mind that Spiritomb isn't affected by normal, fighting, or psychic.)
Aaron-I personally thought Aaron was a walk in the park, my Staraptor beat him easily. No difficulties there.
Bertha-a bit more difficult, but Sudowodo and Golem were taken out easily by Infernape, and Quagsire, Whishcash, and Hippowdon by Roserade.
Flint-Wasn't too hard, mostly because I had the type advantages, Quagsire took care of Rapidash and Infernape, Infernape took care of Steelix and Lopunny, and I used Weavile (using Dark Pulse) against Drifblim.
Lucian-Lucian was, tough, I guess, but mostly due to his Bronzong. Weavile beat Mr. Mime and Girafarig easily, with a little more difficulty on Alakazam, but Weavile beat it nevertheless, Staraptor beat Medicham, but wasn't effective on Bronzong, so I used Infernape, though Bronzong nearly fainted it with Psychic, and it took a couple of revives and hyper potions before I beat Bronzong mostly because of that stupid Psychic attack. I defeated it in the end with Infernape though.
Cynthia-Cynthia was definitely hard, Spiritomb, I just pummeled it with my strongest attacks from Infernape and Staraptor in order to defeat it, but it actually does help that Infernape was a higher level. Garchomp wasn't too hard, cause I took a chance and sent out Weavile to use blizzard, which beat it after two hits. Roserade defeated Gastrodon and Milotic, though for Milotic my Raichu, which had been sitting in its pokeball the whole time, had to jump in, Roserade I defeated with Staraptor, and Lucario with Infernape.
Well, there you go. I think that's pretty close to what I did, cause I can't really remember it like, crystal clearly, but yeah.