for barges and lotia you just need everyone at lvl 30 or so , so they can tank the atacks while tori procs the poisen. poisen does like 10 percent of anythings hp.
so u just wait and defend intill they are at low hp and kill them
and also after reaching the final part of the game its not that bad. every combat encounter is 1 lvl up due to the rideclous xp. and sorry i just found out you dont have to be lvl 99. i did it on a lower lvl with imos as lvl 80, all that is needed is for imos to have the venge barrage skill because his the second most important person in your party there besides the dragon girl. i forgot her name..
imos has a skill called overdrive that makes him immortal and enter a state similiar to the barges or thrash 1v1 fight. making him basicly your dps sorta, because even though the dragon does more damage she has to switch between defending and etc to survive while imos can just spam atacks and not care for 5 turns before becoming crippled and dealing no damage and getting 1 shotted. so basicly u gotta save those dragon tears for the dragon girl and mainly imos for the final fight of that chapter.
also btw phencice flag is just something related to the final part of the game . you need to pick step forward when first meeting phenice is all. this will give you a choice at the end to pick end 6 instead of 5