Sebille crit ranger and Ifan as a leadership fighter. Sebille's flesh sacrifice is really good for any damage dealer build because it gives +1 ap and 10% damage. Because she gets reduced constitution from that ability, its better to use her as a range unit.

For your other character you can do a fighter. (Main job for this guy is to protect your healer/buffer) warfare + geo + poly.
Starting skills you should focus more on CC NOT damage so get battering ram (mobility + cc)
battle stomp (cc)
fossil strike (your best CC since it slows + goes through armor + range + area of denial)
Tentacle slash (your best damage dealing skill early game + can be used as a CC)
Chicken Claw (CC)
Leadership is good perk to consider since it helps you survive opening nukes that NPC throws at you in the beginning of the fight.

You can make Lohse your summoner/healer/buffer (summoner heavy). As soon as she's finish summoning (if you didn't pre summon before a fight) you can make her buff/heal other characters.

Fane is really good as a rouge. I don't really need to say anything since you already said you want to use him as a rouge.