I haven't hit a game over screen yet. But, I've had to run out of the last couple of dungeons multiple times because a party member goes down and there's seemingly no way to revive them this early in the game. I'm not very far in yet. Just got Rika and Seed self destructed.
I think I made it shortly after
as a kid. Don't know how far in that was. I don't want to lose her. Her basic attacks hitting every enemy is the shit.
At this point in the game, Hahn should be carrying shields and using magic only. Rika should be handling most healing duties, but she can't revive people from death. (Chaz learns Rever for that, but I'm not sure at what level.) It's debatable as to whether Alys should dual wield boomerangs or go with 1 boomerang + 1 shield; I prefer the former since she's not that frail, but the damage boost isn't amazing either.
Not sure if you're aware, but the order of your party matters. In battle, the enemies' single-target attacks tend to skew toward your party lead, so it can help to have someone with high defense, HP, or specific resistances in the front. On the other hand, the chance of an ambush at the
start of an encounter is dependent on your party lead's speed; if someone fast is in front, then you have a high chance of getting a freebie turn, but if someone slow is in front, then the reverse is true.
PSIV is usually a war of attrition. Don't be stingy when it comes to spending TP in dungeons; it's usually appropriate to dedicate about half of it for the dungeon and half of it for the boss. Also remember that multi-target skills really should be used liberally throughout dungeons; very few boss encounters have more than 1 enemy present.