I would say you should play an arcanist.
Witch and oracle are already there as companions. If you like Ember I think it is not a good idea to have 2 witches in the party. If you are good you might not like Dearan, so oracle may be fine too. Skald is a bard who can inspire rage with his songs. If I understand the rules correctly party members cannot cast spells when enraged by the skald. This may be a greater downside than the bonus for fighting enraged. If you do not enrage others it would be better to use a normal bard.
Arcanist: I would take a white mage who can turn his spells into cure spells similar to a cleric. He can even resurrect others later. Healing others is a good action, I guess. So you have the full casting power of a wizard and you can also heal other party members. You still need another support caster in the party because you do not get divine buffs or spells that cure bad status effects such as restauration.
Skald: Like I said, unless you want to enrage your entire party often you better take a bard.
Oracle: Personally I would like two options:
- Nature oracle with animal companion and summon spells. You are a druid based on charisma and with cleric spells instead of druid spells. No shapeshift but also no restrictions with alignment.
- Battle oracle with heavy armor, martial weapons and weapon specialisation. You are a warpriest, but with full spell progression up to lv9 spells. Wolf scarred curse gives you a bite attack and your self buffs could turn you into a fighter with full healing/buffing power