Viktoria, I used golden armor and siren esper to upgrade slash resistance ..
because the base missile resistance is already high, so I don't think it needs to be buffed
Use Passive HP up and Self sacrifice for PvP
Self sacrifice and thief lore for PvE ( More Agility )
If you make Vik slightly slower then what ever you are countering her jumps will be consistent in pvp. There is a patch in jp to stop AI using jump if target turn comes before jump CT. I had very good results leaving her at 81 agi to counter gunners in high end arena. If you got a decent Ice Lance you really don't need self sacrifice to 1 shot gunners.
In an arena setting, Viktora has the highest damaging attack in the game (9400) when facing an opponent with 50 Faith, 0 Def, 0 Res. She doesn't have Def Pierce, but is an incredible unit nevertheless.