Revenge Aura Frontliner
There are two possible candidates for this slot and it's Berserker Freya or Berserker Leah.
I do recommend Leah instead because of her higher proc chance and higher ATK % trigger. My logic is that, instead of CC'ing the enemy, you want them dead ASAP. It's easier to prevent the enemy from continuing their trigger fest by killing them than stunning them and trying to deal with it again later, so it's like a "prevention vs cure" kind of thing. I chose prevention which is Leah.
Berserkers are also ideal with dealing against multi-tank teams making this build really versatile.
As for faith and gears, you'd want them to be really tanky so kratos faith and full trinity gears is ideal. Dodge rune is also a must have because you want them to be able to soak as much trigger fest as they can before they go down from taking too much damage.
2nd Row Aura Slave
This is actually not really tricky. You would simply want a unit that has a persistent aura that boosts DEF and ATK. DEF to prevent your squishy 2nd row dps getting sniped. ATK to make your 2nd row dps more consistent at killing whenever proc'ing the revenge aura of your frontliner. For this role, we have SW Teresa, CK Victoria and CK Darrion.
Definitely the best unit for this role is Darrion, his aura has the highest % increase on ATK/DEF. He is a valiant with better stats than usual, DEF is also really easy to boost. Chaos Knight skill (tile swap) is also one of the best utilities on arena.
As for faith and gears, Teresa should be aiming for highest possible MAG with athena faith, full wizardry and full energy runes. Both CK should just aim for kratos faith, full trinity/defense and full guard runes.