My two cents on difficulty.
I really don't think the leaders got that nerfed. I've only played them in E14, but I'll use shofu as a measuring stick, who had no problems against pre-"nerf" Aya and pre-"nerf" Noel, while getting badly beaten by Luna and Samson, who had the fields with them. I just think that the teams were a little bit nerfed to balance the introduction of the Field Effects, with the fight staying about as challenging. Ok, Noel now has no tools against steel, he needs some more fire in his team (Pyroar?), but his healing field greatly helps his ace Clefable if not destroyed, and even if burned, it puts more pressure to the non-Magic Guard user. Aya got underleveled, but she doesn't have to deal with EQs destroying her whole team other than Gengar.
And Hax Queen Serra with Hail + Snow Warning is actually the first time a leader team was helped by its surroundings. Kinda like the Field effects.
As of Charlotte, I didn't play her when she opened with a Ninetales, but she's also better off now. Hits a little bit weaker in the start, but Darmanitan gives her a little bit physical attack, the rest is 5 special attackers. Imagine starting against the old Charlotte with a Prankster with Light Screen/Rain Dance and a Blissey with Heal Pulse, Softboiled and Light Screen. The Prankster sets the first screen or the rain and dies, and Blissey spends all of the battle healing itself or its partner with both moves and potions, or putting a new screen. She needs one more tool against special walls.
We learn, bit by bit. We learn that this monster of a Cradily can be one-shoted by a prepared Fury Cutter. We learn how to deal with all the threats coming our way, we adapt and when we replay the game, it seems easier. I'd like to see an expert mode where all the leaders get a buff, be it getting some levels up, getting more fully evolved Pokemon (for the ones before Kiki), and some fields get more adverse or haxy. But we're currently fine.
And Charlotte is great. A great spook story. Cradily is a great spook story. But we can bring them down very easily.