Question for Skill Inheritance

Vantage should've been given to someone else as Robin has better options out there, swordbreaker and triangle adept was what you should've focused on your Robin. I'm saying vantage is a bad idea though, but I think you had better options for Vantage to be used on. Tharja and Nino I personally haven't used yet due to my unlucky rolls and Olivia I mainly use as a support unit for her dance ability so figuring out what to give her is a bit tricky but might not be necessary.

Ugh, Tharja and Nino? Lucky. I only have Nino.
Anyway, all of your C slots better be buffs with this team. Depending on maps and config you could leave Nino and Olivia the way they are (Olivia gives Nino hone atk and Nino gives Tharja hone atk) or give one hone spd. Then give Robin either hone def or hone res depending on what you struggle with and what you have, and Tharja hone spd to help both Nino and Robin.

Glimmer is a good skill for Nino since it has a low charge count and does good damage. I also like Death Blow 3 on her. Haven't come up with a good B slot skill yet...

As for Tharja she already has a good A slot but consider green tome breaker if you can find it for +spd spd boosted Ninos like mine who will double your Tharja during my turn even if she is +spd. Then if you don't get much use out of her special I would once again suggest Glimmer.

Robin...either swordbreaker or bowbreaker but honestly if played right Nino will easily oneshot most Takus so swordbreaker will probably be better.

In general, Fury3 is the best slot A skill because it raises base stat totals, raising the Arena matchup level and thus increasing your score. The +3 to four key stats very frequently can prevent getting doubled, doubling on enemies, not dying to damage that normally would have killed you. If you have 2 HP and Fury's -6HP triggers, you will be left with 1 HP.

If your character wants to go offensive, Desperation B slot is best, because it synergizes with Fury 3 to get to that magical <75% point where you start doubling everything. With Olivia to help one character attack twice, Fury can -12 HP and trigger Desperation to be ready for next turn...and then that one character can sweep the entire enemy team. In particular these two skills are good on Tharja and Nino, since they have the highest damage potential and won't have to worry about winning speed tiers with desperation active. So if you have Fury3 and Desperation3, prioritize putting them on those two, and settle for competent replacements for Robin if you run out. For Robin(M) Sword breaker is a great substitute, since he's the designated sword killer and this enables him to ORKO swords despite his average speed. You could also consider Triangle Adept in place of Fury, since Robin has two effectivenessess vs colorless and red. This is a LOT more damage than what Fury usually provides, at the expense of not raising BST by 12. A Robin with +40% ATK from weapon advantage and triangle advantage is 56 ATK, which is actually slightly higher than a nonbuffed Tharja or Nino hitting their respective green and red enemies. For Slot C, Olivia is potentially set with hone attack.... While I havent tested it myself, it is suggested that passive Spur skills DO stack. While you cannot have two olivias both honeattack a robin for +8, setting two olivias with Spurattack next to robin will, supposedly. This means you could keep HoneAttack on Olivia, and run SpurAttack on the other three.... Also keep in mind that attack buffs on Tharja and Nino are twice as effective due to their weapon passives. So +4 attack actually translates into +8.

For support skills, olivia has dance... draw back should be run on everyone else for its unparalleled re positioning value. At this point you've probably run out of SP, but the theoretical damage output is so obscene you probably wont need any special skill triggers.