To answer your main question : no Vog is not overrated. It really is the best swordsman armor for FSC.

First, the most dangerous thing in FSC is Fire. You want fire resistance at all cost, because it does a lot of damage and it's everywhere. Vog have Fire resistance.

Second, despite the presence of numerous undead, it's arguable if elemental is not more important shadow. A lot of things deal elemental damage : fire tiles, fire traps, flame throwers, Vanduke mask. Those are arguably more deadly than undead (as a matter of fact, I never runned FSC with a shadow armor, and don't really feel the need, on the other hand I curse myself for not getting fire, and elemental is nice, especially for the mask). Note that it's WAY less important than fire.

Lastly, Vog benefits to swords with a ASI bonus. Since SK is an offensive oriented game (at least the PvE part), you really want those sort of bonus.

Because Blitz have the single most obscene dps on Vanaduke, as well as going through the fireballs (at least most bullets will hit).

Also, it pairs well with Shivermist because it does short burst of very heavy damage, leaving Vanaduke frozen most of the time.

Seriously...go for full vog if you're planning on grinding FSC (assuming you're a swordmaster) and like Bopp said, How are you going to get CoA without defeating vanaduke a number of times to get tokens for blackened crest? I would suggest BTS if you're a swordmaster since it gives you extra sword damage or go for grey owlite as it gives pretty good defense.
As for weapon loadouts (swordmaster):
-Elemental Sword: DA, Voltegde, Glacius, Combuster(despite the fact that it can't deal fire stats, it still does quite a lot of damage)
-Gun: Blitz Needle>AP
-Bomb: Shivermist Buster (For Vana) or Electron Vortex (For levels leading up to D28)
-The last slot is optional but I usually bring my final flourish or a normal-type weapon
If you need help on anything feel free to add, IGN: Corefinder

Here is what i suggest:
Sword:Glacius
Gun:Blitz Needle
Bomb:Shivermist Bust
Armour:Vog Cub
Shield Grey Owlite Shield

I remember the time when I had decided on my first Vana set.
Skelly is not recommended, but if you want, go for it!
Rather, get fire resistance.

A good crowd control elemental weapon is ESSENTIAL when it comes to Vana.
Brandish lines are a prime example of this. Brandish lines are ridiculusly easy to use, as they are regular speed, pretty good attack, and awesome charge.
Combuster is meh, even though thats the one I picked, so Glacius and Voltedge is more recommended.

Do you want something more knockback-ish? Go Divine Avenger; I'm glad I decided to switch my regular elemntal sword, Combuster, for DA. Divine Avenger, although slow, is powerful in both charge and regular attack, and provides some great knockback.

Blitz Needle I've always looked at as the noob weapon, but I still use it just 'cus.
Blitz Needle is something I use to kill wandering off slags and trojans. If you're gonna focus more on slags, and less on trojans and Vana itself, don't bother using this weapon, as it leaves you extremely vulnerable.

Ah. My trusty sidearm gun. When I go on Vana runs, I use my sidearm gun about 33% of the time. When you're at a distance, don't wanna go up to a slag, but still want to deal damage, sidearm guns come in real handy, well, for me anyway. My sidearm gun for Vana is Polaris or AP, normally AP(Argent Peacemaker). Argent is very powerful against undead, not to mention good DPS and quick reload. Unlike Blitz, this one you can move while firing, so it allows you to relax a bit more. Like I said before, if you're more of a knockback kind of guy, go Polaris instead of AP, they both make good sidearms.

Then there is the utility bomb. Utility bombs I use when there is a horde of zombies, and you want to weaken them all at once. I like to use Shivermist Buster, because it leaves slags helpless and just waiting to be charge attacked, by Brandish line, DA, or even Blitz. There is plenty of utility bombs to choose from, like Vortex bomb, Stagger Storm, or Venom Veiler.

The shield is a problem. How can you get Crest of Almire without doing the mission in the first place? Dread Skelly Shield actually might be your best bet and best substitute because its the only shadow shield I can think of at the top of my head right now. Volcanic Plate Shield also works very well, as it has fire defense, as well as Grey Owlite.

Next is the armor set. I'm just gonna mix helmet and armor together on this one. First of all, piercing defense isn't exactly the best way to go for Vana.
Elemental and Shadow defense is what I'm thinking, and the first thing that comes to mind is Divine set. Divine set is EXCELLENT for Vana because it has fire resist, provides great Elemental and Shadow defense, and the Divine Veil provides a damage bonus against fiends, so the damage bonus will help against trojans and Vana itself. The problem is that it has no defense against Normal damage, so I recommend a hybrid, like Divine Veil+Dread Skelly Suit or Vog Cub Coat( Vog more recommended.)

Lastly trinkets. Trinkets aren't really important, I guess, but I'll mention it anyway. Heart Pendants are the first alternative, and usually most common. If your the guy who's always itching for a Vitapod, get Heart Trinkets. Then there is Wetstone Pendants. If you hate fire, get these. Finally, there is Skelly Charms. If you want extra defense against slags, get these. And you most certainly create hybrids, like 1 Heart Pendant and 1 Wetstone Pendant.

Final Outcome:

Sword:Glacius/Voltedge/Combuster/Divine Avenger
Gun(1):Blitz Needle
Gun(2):Argent Peacemaker/Polaris
Bomb: Shivermist Buster/Venom Veiler/Stagger Storm/Electron Vortex
Helm:Divine Veil/Vog Cub Cap/Dread Skelly Mask
Armor:Divine Mantle/Vog Cub Coat/Dread Skelly Suit
Shield:Dread Skelly Shield/Volcanic Plate Shield/Grey Owlite/Crest of Almire(when you are able to get it)
Trinkets:Heart Pendants/Wetstone Pendants/Skelly Charms

Hope this helped :)

Perfect mask of Seerus (If you don't have OCH, just use the Vog Cub Helm. of Volcanic Demo Helm if you're a bomber)

Vog cub Coat (or Volc Demo suit)

Crest of Almire (Or Grey Owlite shield for starters. They both work pretty equally in FSC so it's a choice).

(optional) 2 penta-heart pendants (or any useful trinkets you want)

Leviathan Blade (tears his mask right up in 3-4 charges per chance to hit)

BLITZ NEEDLE. This is a must have weapon for when you're in Vanaduke's room. Also useful for dealing with Trojans (SPOILERS!) if you can out-maneuver them.

Shiermist Buster (It's optional but it's HIGHLY recommended for crowd control).

Argent PeaceMaker (It's optional but it's useful for dealing with Slag Walkers. Heck, since it's the final boss level you can bring any item down there for heating/forging. But bring a good elemental-inducing weapon if you're doing a fully prepared run).

Any Battle Sprite will do (I have Maskeraith)

Perk: Ghostbuster (Excorsizer doesn't really work on Vana)

Harness: Golden (piercing). (Only equipable by Seraphynx and Maskeraith. Piercing damage is Vanaduke's weakness). Or if you have the Drakon, use the Crystal (elemental) harness.

Hope this helps :3

Id have to say as armor, helm or even full set chaos is great. I know many people say the negative resistances way out the good but negative resistances make you a better player in dodges status traps and learning to dodge.

Chaos has charge time reduction med and damage med for all wep types per piece so you could mix it with vog to balance out fire res or get full chaos becuase its pure awesome

As for weapons in fsc get blitz and or shiv
Any of the elemental brandishes
(all work amazingly with chaos)