Exp shortage indeed limits variety, but it may also force you to run back to the Grand Hall or Circus rebattlable trainers to keep up with the level cap and have better chances at winning. That's what most trainers do, and it gets tedius after a while. Sure, strategy beats brute force anytime, but if we were to argue in favor of more strategic plays from the leaders instead of leveling them up to improve their performance, we should better look at improving the AI and creating original strategies for every single leader. If however we are going to buff them the natural way (without of course limiting their strategy), we need to help the PC improve.
Being encouraged to use more pokemon because of how much Exp would otherwise be wasted is a good thing. I would like to know the reasons this didn't work in hardcore, because you use "zero effect" and "really good move" in the same sentense which confuses me.
Are you saying that the conventional EV spreads we use for competitive battling when teambuilding in PO or Showdown are ineffective in an in-game environment, or that the process of relocating the EVs is time-consuming? Either shouldn't be a problem. One is just tedious and has you re-write the code, whereas the other can be solved by doing a bit of research for what's good to use and have a damage calculator by your side to speed up the process.
It's starting to get easier because the game becomes complete, most pokemon are available, and their natural movepools allow them to do their roles just right, without having to rely on EV training, IV breeding, or TM usage. While the first 2 are possible, in a finished game, people won't always take some time off the main story to specifically grind for EVs or breed extensively. Usually you'll only see them grind for exp, which is common in the environment of an RPG game.
As I see, the fields are progressively becoming even stronger, and the leaders' teams are as strong as the pokedex allows them to be. I suppose your statement of "bending the rules" hints to using legendaries, and I would agree that this would make their teams far stronger. However they already have so much to help them against the PC, it's redundant; field effects, access to all items and TMs, Mega Evolution, etc. They even can use pokemon that are limited by the next level cap (since technically, they already own the badge you need for that).
Even so, I would have to pray for Hardy. Unless Gen7 (or Cepheus) brings a Mega Gigalith or awesome Rock types he could use (since he cannot use Diancie or Terrakion), he is going to pose little threat to the player's team. Right now it's pretty much confirmed he's using M-Aerodactyl (so don't expect Scizor anytime soon), and that's pretty much all he has.
I know Adrienn is more likely to be the one we fight this episode, but even xe has better chances thanks to most usable Fairies being non-legendaries, since xe has a M-Mawile to use (xe doesn't know what Gardevoir can do), Azumarill, Togekiss, Granbull etc
Place your bets and get a Nomos doll . . . only for 1.000.000.000 pokedollars