Niam's death felt a bit off to me, in that one didn't really have the chance to see much of her character and motivation, and the motivation she did have, finding a cure for her sister, goes unresolved. Since the group doesn't find a body though, who knows what surprises might emerge later on in regards to her apparent death.
Her death seems to mess quite a bit with the party dynamic, since she is the only dedicated hunter (unless the player themselves goes hunter) which leaves the player with a fairly narrow skill-set, in my case two mages and two melee fighters. All that said, my ignorance of the next three chapters could make this criticism invalid.
I didn't have much difficulty in completing the 9 combat trials, though I did have to reload once when I discovered the poison from the grate traps lasted for the entire combat. Once I knew that, the trap levels were very easy to win, since enemies could pretty much kill themselves on the traps as they tried to reach my party.
Mechanically, I'm not sure how well a dedicated mage will work out in future chapters, since the fourth tier spell variants, already very costly to unlock in terms of AP, drain mana very quickly. Increasing one's total mana supply is also very costly. Maybe consider having some equipment that increases total mana, if you haven't already? The AP regen staves are already very cool, by the way. Also, in the multi-stage fights, I found drawing out a fight with only one or two opponents remaining on the battlefield allowed me to regenerate enough mana so that both my mages were at full. You might want to find a way to curb this, or offer more ways for spellcasters to be at full in the next fight (Although how you would do this without changing the difficulty I don't know), since it's a dull but effective tactic. (Maybe a turn/time limit for some multi-stage combats, before enemy reinforcements arrive, or before something occurs that the players are trying to prevent. Of a similar vein to the baroness rescue)
Others may not agree with this, but at the end of the game, I would very much enjoy having a range of customisable, meaningless fights to test out the limits of my party, since the combat mechanics of the game are very robust.
Overall I was fairly content with the scope of chapter 2. I understand that chapter 3 is significantly more meatier, and as long as there's a range of interesting sidequests to do, which contain some nice choices and consequences (Potentially impacting on the main plot?) I don't think it's necessary to have a bunch of sidequests in chapter 2, especially considering the party are slaves at the time.