I enjoyed the chapters where the castle gets attacked a second time and the little detective bits afterwards.
Calista finally came a bit more into her own, which is great as I found her damsel in distress role becoming boring. Her sleep arrows are ace.
She also learned the barrier spell which made her a fixed party member in battles.

I loved the little cut scene with Mirania in the library, I dunno there was something so atmospheric about it.

Poor Ashtar though.

I didn't wanna say it when you mentioned the obvious twist but I had an inkling and now it's pretty much confirmed that my baby boy is a traitor (or at least madly ambitious). I hope I don't have to kill him in the end.
I'm stuck now too.

Working the arena to level up, shame you don't get EXP when repeating dungeons, that would make it less monotone.
Oh here's my crew (I changed around a bit again):

Zael:Cloth Armour/black & silver
I left one piece of armour on the arm, sorta looks cool. I think silver goes with his hair.

Calista: Brave Armour/red
I kept half the armour on as I think it toughens her up.
Red makes her appear less innocent.

Dagran: Feather Armour/orang
Judging by his hair he is the most stylish of the gang, so he gets the most stylish and modern armour.
Orange goes with his slightly oriental appearance.
Dagran is too hardcore for any armour so it had to go.

Mirania: Heavy Armour/green
As the least girlie of the bunch and an outdoor type an armour that covers her fully suits her.
As you said I agree green suits her nature-spirit and mystical aura.
Again I left a little bit of armour on her arm and shoes to make her look a bit more cool/tough (also the silver sets a nice contrast)

Yurick: Leather Armour/blue
As with Mirania, an armour that covers him fully suits him as he is not as hunky as the others. I also think it makes him look smart and classy. Blue fits his distant persona. I left all the armour on as it doesn't stand out as much anyway.

Syrenne: Hunters Armour/purple
The slutiest outfit for the slutiest girl. Too gay for the male cast and not suiting the other 2 more innocent girls this sorta makes her the default wearer for the outfit. I counterbalanced it by giving her a calm purple.
Some armour left to make her appear at least somewhat as a fighter and not just a pole whore.

Lowell: Stealth Armour/yellow
Every heartthrob looks dashing in a turtle neck.

I left the armour completely on as I think it gives him a prince charming touch (probably the shoulders). I just tried yellow for fun but I think it suits him rather well.