Aaron: This is an unfortunate case. He's packing Heracross, one of the best bugs, but it's nearly useless in the Elite 4 environment because most players will outrun it too easily and hit it hard. Drapion was decent, but the rest of his team is borderline pitiful. He could have been slightly better if he'd started out with a Forretress and set up Stealth Rock/Toxic Spikes.
Bertha: Hippowdon Whiscash, and Quagsire, her three pokemon who could take a hit, were easily her best. Everything else went down too fast. She could have been a lot better if she utilized Sand Storm before the end of the match and had a full-blown team that made use of the move. Cynthia has dibs on Garchomp, but Bertha would have been well off with a Flygon. Of course, the Elite 4 aren't actually capable of using any strategy aside from sending pokemon out, but it would be nice if the CPU were as intelligent as the higher stages of the battle tower.
Flint: This guy isn't traditional Elite 4 material at all, but I kind of dig that. Too bad he doesn't have many useful pokemon besides Infernape.
Lucian: The Bronzong/Mr. Mime combo is the closest thing I've seen to strategy in this Elite 4. He was a decent member, but I think it would have been completely fair to drop Girafarig in favor of a good ghost with a psychic type attack. All in all, he's okay but he's no Lance.
Cynthia: I think her team is well balanced enough but the dumb AI holds her back.
Personally, I don't think the Elite 4 was ever meant to be very challenging. It's part of the storyline that you must complete before you get to the battle tower, the only difficult part of the offline game. If the Elite 4 were actually hardcore, some people (I blame the children) would be stuck until they leveled up properly or just quit playing.