I've done a few Vanaduke runs with parties and I realized something, I'm more of a support in FSC than anything else. Yeah, if i'm careful I should be able to solo FSC but I won't be able to fight Vana if i'm alone because I have no weapons that can reach him (mostly concerned with the final phase). here's my equipment that i use:
Weapons:
Leviathan Blade (Bonus vs Fiend: Low)
Shivermist Buster (Damage Bonus vs Gremlin: Low)
Radiant Sun Shards (Damage Bonus vs Undead: Low)
Sheild
Dark Thorn or Grey Owlite (switch between them)
Armor
Volcanic Demo Helm (Shadow Defense Medium)
Volcanic Demo Suit
And here are some weapons that I have that will be useful in a Vana run.
Kilowatt pulsar (soon to be gigawatt)
Blizzbrand (Damage Bonus vs Fiend: Medium)
Master Blast Bomb
Sealed Sword (soon to be Avenger)
Antigua (soon to be Silversix)
Callahan
Graviton Bomb
Lightning capacitor (soon to be plasma)
Dark Thorn Blade
The current set I have now works very well (Shiver+Levi+zombies= carnage and RSS work just fine with or without shiver) blade but at times i feel like i'm being carried by the group. It seems that a sword-bomber is not a good combination for this. So i guess my question is "Should i invest in some other equipment just in case i am the last one alive or try FSC solo?"
If you ever feel the need to solo Vanaduke, make an Argent Peacemaker or Blitz Needle. If you get good with either of those, they make the Duke very doable alone.