Luna's team is pretty bulky , two of her Pokémon have Moonlight which is boosted by the field and heal 75% so try to have toxik on your toxicroak. Her other mons have night slash or dark pulse boosted by the field and are bulky but they are all slow so I think all your team can outspeed them. Just train them to lv.60-62 and you can beat that leader but the next gym leader is just after that battle and you can't return to reborn city so be sure to have what you want before you go at the next city.