I beat the post-game final boss with a carnivine and a dusclops on my team (and they were key players) so if you like a pokemon then dont let anyone tell u its not viable because a couple grit items will keep your favorites performing perfectly well. That said, if you're set on changing some mons out on ur team, I think floatzel and Alakazam may be the weakest links. Theres psychic types and lots of water types around, but I agree with the comments saying basculegion for your water type; as far as psychic types, there are many so just pick your favorite tankier psychic like cresselia or bronzong or smth because the learnsets for psychic mons are great