Here's my strategy: D goes slayer / thief to max out in strength and speed. Be sure to get Cleave and Barrage as they are the main farm tools and damage dealing abilities.
Now build Lina as a dedicated healer, because the last boss battles require at least one of these. You can in the low levels still use her as a steal machine to farm scrap metal and materials for weapons. You should only spec her into magic / speed in the classes healer / elementalist. Trickster doesn't work in my opinion, since most bosses are immune to debuffs.
Lina will be your second elementalist / healer. You will primarily spec into elementalist for that sweet magic damage.
Kaz is where the plan comes together. I build him as a buff machine/tank by going into Guardian for attack up all / magic up all and then use Guard to attract the unwanted damage. You can either build him as off healer or chain stun with barrage. He is built primarily HP, then speed and then magic if off healer / attack if damage.
Well that was nice. I hope this gets badges. Perhaps you should make the time slot a bit harder to finish. Anyway I played all the levels to perfection. Maybe think about adding something at the end when everything has been cleared? That would really make you think: I accomplished this, yeah!
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