I can agree with all of your Battle Maison/Frontier/Tower/Subway/PWT grievances.
Last night I was doing Rental Master at the PWT and every time I lost, the AI scored at least one crit. They then swept my team. Mind you, I tried Rental a good 6-7 times before quitting after sheer frustration.
Recently I got the highest streak ever at the Battle Maison...38!!! I did the same deal as Water Master Tsunami and interrupted for a quick breather, and then entered again with the same team, Mega Kangaskhan, Talonflame, and Greninja.
Mega Kanga gets downed by a Mandibuzz with 4 status moves. It consisted of it hitting itself four times on confusion while being poisoned. It dies in five turns.
I'm like, "Ok, that was stupid, but Greninja'll do great. Greninja slaughters the Mandibuzz. Next Pokemon, Heracross. Not wanting to switch out (I'm very conservative in the Battle Maison, I rarely switch), I Scald it. It does like 1/3 of his health. It Megahorns, and luckily I have a Focus Sash on my ninja. I Scald again, it's in the yellow, and it kills me with Megahorn.
Talonflame wrecks it with Brave Bird.
He then sends out Pyroar, which Greninja would have destroyed. -_-
I Brave Bird, and it doesn't die. I take massive recoil and Life Orb damage, and it Hyper Voices for the win.
Needless to say I am done with post-game AI battles. I tried again and I got to 34 before losing to the same Heracross.