Snowbreak: HCL6-4, Trial and Error
This one stumped me for a awhile but I was just apparently doing it wrong.
The hard part are the two flying(Mimir) ones at the end. The first two are easy enough to kill. Once the flying ones(Mimir) trap you in their barriers the mobs can shoot you to death as you can't dodge. the big guys aren't a problem as they are easy enough to avoid and sluggish in their attacks.
Problem is killing the mobs causes them to respawn. I have tried but my friend noted that after you kill enough ,they do in fact eventually stop. I reconfirmed this is the case and also noticed if you kill the big guys(Bing-type), they will also cause the ranged units to respawn. So best to just kill only the ranged guys(Jia-type) until they stop and leave the big ones alone. I assume all the mobs will eventually stop respawning but there's no real reason to bother killing all of them.
So the key is kill the first mini-boss(Gamir). It's the deadliest due to being able to charge and suck you in. The 2nd boss is easy to just kite, and its ranged attack is easy enough to avoid. During the 2nd boss, kill all the ranged units, once that is done, you can finish off the 2nd mini boss(thjazi). The two flying(Mimir) ones will then spawn. Unless you got maybe Fenny, you can just ignore the barriers and wait until they despawn. Just focus on dodging during the barriers. Also pay attention to the cube spawns, kill them ASAP if you see one, if you get trapped while its still alive, its basically gameover.
Lastly, if you need to heal, just switch characters and wait until all 3 are low before using the heal so you maximize its effectiveness.
