Dragoon
Inquisitors
Grand ranger
Sharpshooter
Ninja
Witch doctor
Use any of them except ninja
Only replace ninja with one of the two healer (which one have less atk) for gold farm and event
This is very good advice.
However, MinMax ... do note there is some disagreement among players on the merits of Gladiator vs. Dragoon for your final Freya-Lancer choice, and not everyone is keen on Ninja, so there's room for flexibility there.
The main issue is that for Dragoon and Ninja, the active skill does move your character elsewhere on the playing field - Dragoon leaps to an empty tile, Ninja swaps places with enemy unit. This of course means your unit will be out of formation and your aura link is probably going to break at that point. That's the downside, and a lot of people don't like that.
However, the counter-argument is that there are many situations where such a teleport is worth it, e.g. D
ragoon can leap closer to stairs during gold mine farm, or close with a ranged attacker in enemy back row. Ninja can swap and pull enemy unit out of formation, etc. Lots of people also like the Ninja version of the aura refresh. Personally I think that stuff is worth it, but if you don't care for that, then don't feel that you NEED to go Dragoon or Ninja. Plenty of people like, say, Gladiator as the end unit for Lancer path.
Separately - assuming an Inquisitor Teresa and Witch Doctor Luthor, there are people who use both of them in same squad for arena.
Inquisitor Teresa automatically heals every turn, guaranteed (I think the heal is herself + others in aura). Witch Doctor Luthor aura has chance to inflict poison when other unit in aura is healed. You get the idea. Luthor isn't the best Witch Doctor, especially not in Zeus faith, but... hey, we work with what we have, yeah?
It does mean you're bringing two healers in your arena team, and Luthor isn't the best unit to choose Witch Doctor on, but it will get the job done. This is considered an arena setup but I imagine it would work in some other PvE content. I haven't tested this personally but am raising a Witch Doctor Luthor to see (I already have the Teresa at 5-star and am working on Luthor now).