I may have been wrong when I said a few posts ago that items like charcoal or mystic water weren't working. If I understood well, in this release, the damage inflicted by a move isn't supposed to be higher then the defending pokemon's max hps, unlike before. Has I've been doing only one hit K.O.s with my Growlith, it could explain why I thought these items don't work whereas they probably do.
Actually I think it's this point of the battle system which can be glitchy at times, using the attacking pokemon's left HP to calculate the damage instead of that of the defending one. Now what makes it ambiguous is that it doesn't happen all the time.